This class action arises out of the termination of post-retirement medical benefit plans, sponsored by Unisys for retirees and disabled former employees of Unisys and its corporate predecessors, Sperry Corporation and Burroughs Corporation. The retirees seek to recover post-retirement medical benefits under the terms of their welfare benefit plans and under the Employee Retirement Income Security Act's ("ERISA's") provisions for appropriate equitable relief.

We are asked to decide in this particular appeal1 whether the district court erred in holding, on this breach of contract claim, that summary plan descriptions that used the terms "lifetime" or "for life" to describe the duration of medical benefits, while at the same time reserving the employer's right to modify or terminate at "any time" and "for any reason" the plans under which these benefits are provided, were unambiguous. We also address whether the district court erred in refusing to reinstate the retirees' estoppel claims upon which Unisys had earlier been granted summary judgment. We will affirm the judgment of the district court.

In September of 1986, Sperry Corporation and Burroughs Corporation merged to form Unisys Corporation. Prior to the merger, Sperry consisted of a number of business units or divisions. Until 1984 each Sperry division maintained its own medical benefits program, with each described in a separate summary plan description. In 1984, in an attempt to streamline the medical benefits plans and in response to rising medical costs, Sperry implemented Medflex, a corporate-wide medical benefits plan that applied to the entire Sperry Corporation.2 Medflex was applied to future retirees only; existing retirees continued to receive coverage under the pre-Medflex plans which applied when they retired.

Following the merger in 1986, Unisys continued the Medflex plan for active employees and for those who retired after its implementation but prior to April 2, 1989. Unisys also continued all of the pre-Medflex plans for those who retired prior to Medflex's implementation.3 In 1989, Unisys effected the consolidation of its retiree medical benefit plans when it created the Unisys Post-Retirement and Extended Disability Medical Plan to cover all employees who retired after April 1, 1989, most of whom were former Sperry and Burroughs employees.

On November 3, 1992, Unisys publicly announced that effective January 1, 1993, it was terminating all existing medical benefit plans and replacing all of the pre-existing medical plans with the new Unisys Post-Retirement and Extended Medical Disability Plan. Under the new plan, retirees would be responsible for increasing levels of contributions until January 1, 1995, when they would have to pay the full cost of their premiums. Thus, the new plan sharply contrasted with earlier plans, under the majority of which Unisys paid the entire premium for an individual's life and provided benefits for the individual's spouse as well.4

The appellees in this case are former employees of Sperry Corporation (and their eligible dependents) who retired between 1969 and April 1, 1989, from Sperry Corporation or Unisys, Sperry's successor. Following Unisys' termination of their post-retirement medical benefit plans in late 1992, the retirees sought relief based on three theories: breach of contract, equitable estoppel, and breach of fiduciary duty. The Sperry retirees argued that Unisys' termination of their respective medical plans violated ERISA. They argued first that Unisys had denied them "vested" benefits in violation of 29 U.S.C. Sec. 1132(a)(1)(B) because the summary plan descriptions ("SPDs") explaining their medical benefits contained the term "lifetime" benefits. Regarding their contract claims, the retirees relied on the explicit lifetime language in the plans, e.g., "when you retire, your medical benefit will be continued for the rest of your life", and on statements made by the company both orally and in writing to the same effect.5

The Medflex SPD is illustrative. A Sperry employee who retired during the period January 1, 1984 through April 1, 1989 received medical benefits under this plan. The SPD for Medflex is set forth in a booklet titled, "Your Company and You." Included in this plan was the following description of retiree medical benefit coverage:

If you're eligible, Medical Plan benefits continue without cost after you terminate active employment. Benefits also may continue on a contributory basis for your eligible dependents who are covered when your employment terminated.... Coverage continues for you for life and for your dependents while they remain eligible provided you don't stop the contributions for their coverage. After your death, your eligible dependents may continue coverage by making the required contributions. Their coverage continues until your spouse dies or remarries.

(A 2227) (emphasis added).

The retirees argued alternatively, that even if the court were to find that "lifetime" is not synonymous with "vested", the evidence established that Unisys intended that a reservation of rights clause in the plan, enabling the company to change the plan at will, only applied to active employees and not to retirees; thus, the company never intended to reserve its right to terminate the plans as far as retirees are concerned. In addition, the retirees contended that Unisys breached its fiduciary duty by systematically misrepresenting the plans and should be equitably estopped from exercising any right to terminate their benefits.6

Unisys responded that it had indeed reserved the right to terminate the retirees' medical plans due to the reservation of rights clauses or "RORs" located in other sections of the plans. Typical of these clauses is the one set forth in the SPD describing the Medflex plan. The Medflex SPD booklet, "Your Company and You," was distributed to all employees and contained the following reservation of rights clause:

The Company expects to continue the Plans, but reserves the right to change or end them at any time. The Company's decision to change or end the Plan may be due to changes in federal or state laws governing welfare or retirement benefits, the requirements of the IRS or ERISA, the provisions of a contract or policy involving an insurance company or any other reason....

(A 2750) (emphasis added).

In addition to the provisions set forth in the summary plan descriptions, information about retiree medical benefits was also conveyed to the Sperry retirees through various informal oral and written communications. As in the summary plan descriptions, the duration of medical benefits was described as being "for life" or for the "lifetime" of the retiree and spouse. Sperry did not include in these informal communications a reference to the reservation of rights clause.

Notwithstanding these communications, Unisys denied having created vested medical benefits through its use of the words "lifetime" or "for life", and early in the litigation filed a motion for summary judgment seeking dismissal of all of the regular retirees' claims based on the unambiguous reservation of rights clauses in the plans. Although the district court granted Unisys' motion on the retirees' breach of fiduciary duty and estoppel claims, it denied summary judgment on the retirees' contract or plan-based claim. The district court initially found that the internal inconsistency between the lifetime promises and the reservations of rights clauses made the plans ambiguous and thus a trial on the extrinsic evidence was necessary to resolve the ambiguity. In re Unisys, 837 F. Supp. 670, 679 (E.D.Pa.1993). After trial,7 the district court reversed its position on both the contract and breach of fiduciary duty claims, entering judgment against the Sperry regular and VRIF retirees on their contract claims but reinstating the Sperry retirees' breach of fiduciary claim.8

The district court had jurisdiction pursuant to 28 U.S.C. Sec. 1331 and 29 U.S.C. Sec. 1132(e)(1). We have jurisdiction pursuant to 28 U.S.C. Sec. 1291.

ERISA is a comprehensive statute enacted "to promote the interests of employees and their beneficiaries in employee benefit plans," Shaw v. Delta Air Lines, Inc., 463 U.S. 85, 90, 103 S. Ct. 2890, 2896, 77 L. Ed. 2d 490 (1983), and "to protect contractually defined benefits," Massachusetts Mutual Life Ins. v. Russell, 473 U.S. 134, 148, 105 S. Ct. 3085, 3093, 87 L. Ed. 2d 96 (1985). See also 29 U.S.C. Sec. 1001. ERISA recognizes two types of employee benefit plans: pension plans and welfare plans. Deibler v. Local Union 23, 973 F.2d 206, 209 (3d Cir.1992). In general, welfare plans provide "medical, surgical or hospital care or benefits, or benefits in the event of sickness, accident, disability, death or unemployment...." 29 U.S.C. Sec. 1002(1). Pension plans provide: (i) retirement income to employees or (ii) result in a deferral of income by employees for periods extending to the termination of covered employment or beyond. 29 U.S.C. Sec. 1002(2)(A). Both Unisys and the retirees agree that the retiree medical benefit plans at issue in this case are welfare benefit plans under 29 U.S.C. Sec. 1002(1).

The implications of this are significant. Although ERISA contains elaborate vesting requirements for pension plans, ERISA does not require automatic vesting of welfare benefit plans. Alexander v. Primerica Holdings, Inc., 967 F.2d 90, 95 (3d Cir.1992); Smith v. Hartford Ins. Group, 6 F.3d 131, 136 (3d Cir.1994). Congress did not impose vesting requirements on welfare plans because it determined that "[t]o require the vesting of those ancillary benefits would seriously complicate the administration and increase the cost of plans whose primary function is to provide retirement income." Hozier v. Midwest Fasteners, Inc., 908 F.2d 1155, 1160 (3d Cir.1990) (citing H.Rep. No. 807, 93rd Congr., 2d Sess. 60, reprinted in 1974 U.S.Code Cong. & Admin.News 4670, 4726). In rejecting the automatic vesting of welfare plans, Congress evidenced its recognition of the need for flexibility with regard to an employer's right to change medical plans. As the Court of Appeals for the Second Circuit observed:

Automatic vesting was rejected because the costs of such plans are subject to fluctuating and unpredictable variables. Actuarial decisions concerning fixed annuities are based on fairly stable data, and vesting is appropriate. In contrast, medical insurance must take account of inflation, changes in medical practice and technology, and increases in the cost of treatment independent of inflation. These unstable variables prevent accurate prediction of future needs and costs.

Moore v. Metropolitan Life Ins. Co., 856 F.2d 488, 492 (2d Cir.1988). See also 29 U.S.C. Sec. 1051.

Nonetheless, in some situations, a welfare plan may provide a vested benefit. Alexander, supra, 967 F.2d at 95; Schoonejongen v. Curtiss-Wright, 18 F.3d 1034, 1042 (3d Cir.1994), rev'd and remanded on other grounds, --- U.S. ----, 115 S. Ct. 1223, 131 L. Ed. 2d 94 (1995). The plan participant bears the burden of proving, by a preponderance of the evidence, that the employer intended the welfare benefits to be vested. Howe v. Varity Corp., 896 F.2d 1107 (8th Cir.1990).

ERISA's framework ensures that employee benefit plans be governed by written documents and summary plan descriptions, which are the statutorily established means of informing participants and beneficiaries of the terms of their plan and its benefits. See, e.g., Hozier v. Midwest Fasteners, Inc., supra; Confer v. Custom Engineering Co., 952 F.2d 41 (3d Cir.1991); Hamilton v. Air Jamaica, Ltd., 945 F.2d 74 (3d Cir.1991), cert. denied, 503 U.S. 938, 112 S. Ct. 1479, 117 L. Ed. 2d 622 (1992); 29 U.S.C. Sec. 1022(a)(1). Accordingly, any retiree's right to lifetime medical benefits under a plan can only be found if it is established by the terms of the ERISA-governed employee benefit plan.

A court must examine the plan documents. Boyer v. Douglas Components Corp., 986 F.2d 999 (6th Cir.1993). Extra-ERISA commitments, such as the right to receive free lifetime coverage, must be found in the plan documents and stated in clear and express language. Wise v. El Paso Natural Gas, 986 F.2d 929 (5th Cir.), cert. denied, --- U.S. ----, 114 S. Ct. 196, 126 L. Ed. 2d 154 (1993). See also Alday v. Container Corp. of America, 906 F.2d 660, 665 (11th Cir.1990) ("[A]ny retiree's right to lifetime medical benefits at a particular cost can only be found if it is established under the terms of the Erisa-governed benefit plan document"), cert. denied, 498 U.S. 1026, 111 S. Ct. 675, 112 L. Ed. 2d 668 (1991). The written terms of the plan documents control and cannot be modified or superseded by the employer's oral undertakings. See Hozier v. Midwest Fasteners, Inc., 908 F.2d at 1163 (citing Musto v. American General Corp., 861 F.2d 897, 910 (6th Cir.1988), cert. denied, 490 U.S. 1020, 109 S. Ct. 1745, 104 L. Ed. 2d 182 (1989) (the unambiguous written provisions of a plan must control, and extrinsic evidence may not be introduced to vary the express terms of a plan)) and Gordon v. Barnes Pumps Inc., 999 F.2d 133, 137 (6th Cir.1993) (a basic principle of ERISA is that a plan may not be modified or superseded by oral statements or other extrinsic evidence).

To determine whether Sperry intended to confer vested benefits upon its retirees in this case, we must analyze the provisions of the retiree medical benefit plans at issue. Unisys and the Sperry retirees agree that the Sperry summary plan descriptions are the controlling documents that we must interpret. The threshold issue in this case, whether the Sperry plans were ambiguous, is a question of law. Taylor v. Continental Group, 933 F.2d 1227, 1232 (3d Cir.1991). We turn now to the exact language of the plans in question and apply these principles of law.

Although Sperry maintained many different medical benefit plans for its separate divisions or business groups, all of these plans conveyed the same message: that post-retirement medical benefits would be provided for life. There were slight variations in the exact language utilized to convey this message. For instance, the Sperry Univac plan contained the following language:

When you retire ... the comprehensive medical expense benefits then in force for you and your eligible dependents under this plan will be continued for the rest of your life.

SPD for Sperry Univac (A 2232). Another plan provided: "... coverage continues for you for life and for your dependents while they remain eligible...." Sperry Medflex SPD (A 2749).

Unisys offered the same defense for all Sperry divisions, namely that this lifetime language was subject to reservation of rights clauses located elsewhere in the plans. Although some reservation of rights clauses were more detailed than others, each clause provided that the company could terminate the plan "at any time" and "for any ... reason." See Sperry Medflex Plan, A 2750. Based on these provisions, the retirees asserted that the retiree medical benefit plans were ambiguous and that the ambiguity arose not merely from the reservation of rights clauses themselves, but also from the inconsistency between the reservation of rights clauses and the plan's lifetime promises. According to the retirees, the plans were ambiguous because they were susceptible to either of two interpretations: the retirees' interpretation that the lifetime language limited the scope of the reservations of rights, or the company's interpretation that the reservation of rights limited the lifetime language. If the court finds "but one reasonable interpretation, then a fortiori there can be no ambiguity." Curcio v. John Hancock Life Ins. Co., 33 F.3d 226, 231 (3d Cir.1994). However, if the language is susceptible to more than one reasonable interpretation, then it will be found to be ambiguous. Id.9

In Schoonejongen v. Curtiss-Wright, supra, we reviewed summary plan descriptions which stated in varying forms that health insurance benefits would terminate "upon death" or when "you cease to be a member of a class eligible for insurance ... [or] upon discontinuance of the group policy." 18 F.3d at 1036-37. Some years later, Curtiss-Wright amended the language in its summary plan description to provide that "[c]overage under this plan will cease for retirees and their dependents upon the termination of business operations of the facility from which they retired." Id. at 1037. The affected retirees argued that this reservation on its face referred only to employees and not to retirees. Because the reservation did not unambiguously reserve the right to terminate retiree benefits, the district court held a trial to resolve the ambiguity. 18 F.3d at 1041. Based on the extrinsic evidence, the district court found that the clause did apply to retirees. We affirmed the district court's holding that Curtiss-Wright had reserved the right to terminate retiree benefits, but held that Curtiss-Wright lacked a formal amendment procedure in violation of section 402(b)(3) of ERISA, 29 U.S.C. Sec. 1102(b)(3), and therefore the amendment to the plan was invalid. We responded to the retirees' argument that the plan's description of the duration of benefits as ceasing "upon death" created vested benefits:

It seems to us, however that our conclusion [that Curtiss-Wright had a reserved right to amend] is a complete answer to this argument. Even if the plan contained unambiguous assurances that all retirees would have health insurance benefits for so long as Curtiss-Wright maintained a post-retirement health insurance program, the general reserved right to amend the terms of the plan in whole or in part would render the right of any retiree or group of retirees terminable by the adoption of a legally effective amendment.

Curtiss-Wright, 18 F.3d at 1042 (emphasis added). Although the Supreme Court reversed our conclusion that a formal amendment procedure was lacking under section 402(b)(3) of ERISA, the Court's decision is consistent with our conclusion that Curtiss-Wright had expressly reserved the right to amend its plan to effect a termination of benefits under the plan, as well as our conclusion that "an important and proper purpose of reserving a general right to amend is to permit the conditioning or cessation of any participant's benefits, not vested by virtue of the mandate of ERISA, in ways not originally foreseen in order to meet unanticipated changes of circumstance." Id.10

We agree with the district court that the fact that the Sperry plans used terms such as "lifetime" or "for life" to describe the duration of retiree medical benefits, while at the same time expressly reserving the company's right to terminate the plans under which those benefits were provided, did not render the plans "internally inconsistent" and therefore ambiguous here.11 An employer who promises lifetime medical benefits, while at the same time reserving the right to amend the plan under which those benefits were provided, has informed plan participants of the time period during which they will be eligible to receive benefits provided the plan continues to exist. In this case, the Sperry retirees' eligibility for benefits was qualified because it was subject to Unisys' reserved right to terminate the plan under which those benefits were provided.12

Other courts have reached the same conclusion, recognizing that an employer can qualify the provision of "lifetime" benefits by reserving the right to terminate the plan under which those benefits are provided. Thus, in DeGeare v. Alpha Portland Indus., Inc., 652 F. Supp. 946 (E.D.Mo.1986), aff'd, 837 F.2d 812 (8th Cir.1988), vacated and remanded on other grounds, 489 U.S. 1049, 109 S. Ct. 1305, 103 L. Ed. 2d 575 (1989), the court found that seemingly inconsistent provisions, such as those permitting modification of the plan and those indicating that benefits last for life, must be construed to be harmonious. The court specifically found "harmonious and reasonable the interpretation of [the employer] of the written documents to provide lifetime benefits subject to [the employer's] reserved right to amend." 652 F. Supp. at 961. See also Anderson v. Alpha Portland Indus., Inc., 836 F.2d 1512, 1518 (8th Cir.1988), cert. denied, 489 U.S. 1051, 109 S. Ct. 1310, 103 L. Ed. 2d 579 (1989) (plaintiffs did not meet their burden of proving vested welfare benefits where an employer promised to provide welfare benefits "until death of retiree" where the employer had expressly reserved the right to terminate or amend the plan); Alday v. Container Corp. of America, 906 F.2d 660 (11th Cir.1990), cert. denied, 498 U.S. 1026, 111 S. Ct. 675, 112 L. Ed. 2d 668 (1991) (where summary plan description also clearly provided that retiree health insurance could be terminated or modified, these terms of description were controlling); Gable v. Sweetheart Cup Co., Inc., 35 F.3d 851, 856 (4th Cir.1994), cert. denied, --- U.S. ----, 115 S. Ct. 1442, 131 L. Ed. 2d 321 (1995) (company's express reservation of its right to modify or terminate the participants' benefits is plainly inconsistent with any alleged intent to vest those benefits).

Here Sperry, and later Unisys, stated clearly and unequivocally in their summary plan descriptions that the company reserved the right to "change or end [the plans]" "at any time" and for "any ... reason." Due to this broad and unambiguous language, we hold that the district court did not err when it concluded that the Sperry retiree medical benefit plans were not internally inconsistent because they contained "lifetime" language but also reserved the right to terminate benefits at any time.

Notwithstanding its legal conclusion based on Curtiss-Wright that the Sperry plans unambiguously reserved Unisys' right to terminate its retiree medical benefit plans, the district court analyzed the extrinsic evidence in order to determine whether the company intended the reservation of rights to apply to the retirees' medical benefits.13 Given the retirees' concerns that Curtiss-Wright did not foreclose the inquiry into extrinsic evidence, and because a trial had already been held in the case, the district court made a factual determination that the reservation of rights clause was intended to apply to the retirees' medical benefits, as well as a legal determination that the retirees had not sustained their burden of proving that the employer intended to vest retiree benefits.

The district court analyzed, first, the extrinsic evidence with respect to the intent of the plan sponsor, Unisys. Although the retirees argued that when the company used the term "lifetime," its true intent was to vest benefits, the district court found that the use of the word "lifetime" did not manifest an intent on the part of the plan sponsor to create "vested" benefits, because the evidence did not support this argument. The district court concluded that because the company had used the word "vested" in its medical plan for its top level Sperry executives, but not in the rank and file plans, the company must have intended not to vest the rank and file benefits. Rather, as the language of the executive plan revealed, when the company wanted to create vested benefits, it knew how to do so.14

The district court also found that the retirees' assertion that the reservation of rights, which did not facially distinguish between actives and retirees, applied only to actives was not supported by a preponderance of the evidence. (A 2278-79). While the court found that the company had "locked in" retirees' benefits in practice in the past, it was not persuaded that the company had embraced the "active/retiree" distinction as a matter of actual policy due to the fact that not a single document corroborated the testimony that an active/retiree distinction was in force; the distinction was not incorporated into the reservation of rights or summary plan descriptions or reduced to writing as an official policy. (A 2278-80). The district court found significant the facts that the alleged policy of restricting the RORs to active employees had never been formally discussed by the Board of Directors, and that a board resolution did not exist confirming the creation of this policy. Id. We agree with the district court that all of these factors militate against the idea that Unisys intended to restrict the application of the RORs to active employees.

Numerous retirees testified at trial that they understood that their benefits could not be reduced after retirement. Indeed, the district court found that there was "no question that the defendant routinely spoke of the medical benefits as continuing 'for life.' " (A 2281). The district court specifically found that "this message was conveyed time and time again through informal communications that were sent out to retirees, and by oral statements that were made to these individuals both at private exist interviews and in group retirement sessions. Id. Nonetheless, the district court concluded that the retirees' reasonable understanding of their benefits must be limited to the reasonable understanding of the summary plan descriptions or plan documents, due to our strong precedent which precludes informal amendments to ERISA benefit plans. See, e.g., Hozier v. Midwest Fasteners, Inc., 908 F.2d at 1164; Haberern v. Kaupp Vascular Surgeons Ltd. Defined Benefit Pension Plan, 24 F.3d 1491 (3d Cir.1994) (and cases cited therein).

Finally, the retirees' submitted evidence of past practice which demonstrated that Sperry had never reduced retiree medical benefits prior to this litigation. For example, when the Medflex plan was implemented, it applied to future retirees only. The retirees argued that this evidence established the existence of a policy pursuant to which benefits were "locked-in" upon retirement. The district court found that "merely because the company had never chosen to exercise its reservations of rights prior to this litigation, did not mean that the company had waived its right to terminate the plans pursuant to these broad and unequivocal reservation of rights clauses." (A 2283) (citing Alexander, 967 F.2d at 93 (rejecting the defendant's argument that the company's past practice of changing benefits rendered the amendment clause unambiguous); and Howe v. Varity Corp., 896 F.2d at 1110 ("merely because defendants chose to exempt retirees from plan changes in the past does not mean that defendants considered themselves forever bound to do so")).

Because the record before us firmly supports all of these findings, we cannot say that they are clearly erroneous.15 Therefore, the district court did not err in concluding that the reservation of rights applied to the Sperry retirees' medical benefits and that the retirees' medical benefits were not intended by the company to be vested based upon this evidence.16

The Sperry retirees additionally contend that the district court erred in failing to sustain the separate contract claims of the "early retirees" or "VRIF" ("Voluntary Reduction in Force") retirees. The VRIFs asserted a claim separate from that of the regular retirees: that the company offered them certain benefits to induce them to retire which they accepted by retiring earlier than they would have. They contend that this offer and their acceptance formed a binding contract, independent of the contract rights asserted by the other retirees founded upon the basic plans. See Sprague v. General Motors Corp., 768 F. Supp. 605 (E.D.Mich.1991).17

Although it is true that the VRIFs retired early, foregoing future salary and pension accruals in order to secure the retiree medical benefits under their existing plans, the plans pursuant to which the VRIFs received retiree medical benefits contained clear and unequivocal reservation of rights clauses that permitted the company to end the plans at any time. See, e.g., the 1988 VRIF offering document advising the prospective participant of the entitlement to "coverage under the Post-Retirement Medical Plan in effect at the time your first [pension] check becomes payable." (A 4395). Medflex, the plan pursuant to which the VRIF retiree medical coverage was to be provided, contained an unambiguous reservation of rights clause.18 (A 3011). While the VRIFs point out that the offering materials for their incentive plans promised the incentive benefits without any reference to a reserved right by the company to amend or terminate the plans, we find that this is not dispositive of their claim because the benefits which the VRIFs were to receive were described in summary plan descriptions containing unambiguous RORs. Consequently, the district court did not err in rejecting the VRIFs' separate bilateral contract claim.

We turn to the retirees' final argument that the district court erred in concluding that the estoppel claims of all of the regular retirees failed as a matter of law and erred in refusing to reconsider its grant of summary judgment on that claim. In re Unisys, 837 F. Supp. 670, 680-81 (E.D.Pa.1993).

An ERISA beneficiary may recover benefits under an equitable estoppel theory upon establishing a material misrepresentation, reasonable and detrimental reliance upon the representation, and extraordinary circumstances. Curcio v. John Hancock Mutual Life Insurance Co., 33 F.3d at 235; Smith v. Hartford Ins. Group, 6 F.3d 131, 137 (3d Cir.1993).19 The retirees contend that they can establish these elements.20

While we acknowledge that many retirees may have relied to their detriment on their interpretation of the summary plan descriptions as promising vested or lifetime benefits, we nonetheless must reject their estoppel claim. Due to the unambiguous reservation of rights clauses in the summary plan descriptions by which Unisys could terminate its retiree medical benefit plans, the regular retirees cannot establish "reasonable" detrimental reliance based on an interpretation that the SPDs promised vested benefits. The retirees' interpretation of the plans as providing lifetime benefits is not reasonable as a matter of law because it cannot be reconciled with the unqualified reservation of rights clauses in the plans.

Our sister courts of appeals have also rejected estoppel claims because of the presence of unambiguous reservation of rights clauses on the basis that a participant's reliance on employer representations regarding benefits may never be "reasonable" where the participant is in possession of a written document notifying him of the conditional nature of such benefits. See, e.g., Gordon v. Barnes Pumps, Inc., 999 F.2d 133, 137 (6th Cir.1993) ("[a]ll plan participants knew or should have known from the express terms of the Pullman plan that benefits could be altered at any time"). Accord Alday v. Container Corp. of America, 906 F.2d 660, 666 (11th Cir.1990) (promissory estoppel did not bar employer from modifying terms of retiree medical insurance plans despite participant's claim that employer induced him into believing that plan's terms would not change; plan unambiguously stated that the employer reserved the right to modify or terminate the plan), cert. denied, 498 U.S. 1026, 111 S. Ct. 675, 112 L. Ed. 2d 668 (1991).

While our decisions have not required an express finding of plan ambiguity as an element for establishing an estoppel claim, we have required that reliance be reasonable. Because our decisions require that any detrimental reliance on plan language also be "reasonable," our finding that the RORs are unambiguous undercuts the reasonableness of any detrimental reliance by the retirees. Accordingly, we hold that the district court did not err in concluding, on summary judgment, that the retirees' estoppel claim failed as a matter of law.

For the foregoing reasons, we will affirm the judgment of the district court.