The district court vacated the decision of an arbitration panel which denied supplementary retirement benefits to three employees of appellant, Eastern Airlines, Inc. (hereinafter "Eastern"). The court held that the panel had exceeded its jurisdiction by failing to apply unambiguous language in the collective bargaining agreement that clearly entitled the employees to benefits. We conclude that the district court erred in vacating the arbitral award, and we therefore reverse its judgment.

The dispute in this case centers around the interpretation of Eastern's retirement plan, established in 1947 as part of the collective bargaining agreement between Eastern and the Air Line Pilots Association (hereinafter "ALPA"). The retirement plan contains two definitions that are central to the determination of eligibility for benefits. Article I, section 1.15 of the plan defines "normal retirement age":

"Normal Retirement Age" for any Participant means the 60th anniversary of his date of birth.

The plan then defines "normal retirement date" in Article I, Section 1.16:

"Normal Retirement Date" means the first day of the month coinciding with or next following the Participant's attainment of his normal retirement age.

The interplay between these two sections creates two possible groups of employees for purposes of retirement eligibility. One group, consisting of employees whose birthday falls on the first of the month, becomes entitled to benefits immediately upon their sixtieth birthday. The remaining employees are not eligible for benefits until the first day of the month following their sixtieth birthday.

In 1977 Eastern and ALPA agreed to provide supplemental retirement benefits for various classes of employees. The plan amendment had an "effective date" of May 1, 1977 and specifically provided increased benefits for employees "who have a 'normal retirement date' on or after May 1, 1977."

The appellees in this case, three retired pilots covered under the plan, became sixty years old after April 1, 1977 and before May 1, 1977.1 According to the terms of Article I, sections 1.15 and 1.16, their normal retirement date was May 1, 1977. Under the plain meaning of the language of the amendment, therefore, they were entitled to supplemental retirement benefits.

Eastern, however, refused to pay appellees the supplemental benefits. It claimed that the intent of the company and the union was to grant the benefits to employees who became sixty years old on or after the effective date of the amendment, May 1, 1977. This dispute was referred to an arbitration panel created by Article X of the retirement plan2 and empowered by Article XI to resolve all disputes arising under the plan.3 The panel, consisting of two members chosen by Eastern and two members chosen by ALPA, heard extensive evidence concerning the intent of the negotiators of the 1977 amendment. The evidence included actuarial projections used by the negotiators to determine the cost of the supplemental benefits that took into account only those pilots who would become sixty on or after May 1, 1977.4 The arbitration panel found unanimously that the three Eastern pilots were not entitled to supplemental benefits.5

Eastern is an air carrier operating in interstate commerce and is therefore covered by provisions of the Railway Labor Act, 45 U.S.C. §§ 151-188. See 45 U.S.C. § 181; I.A.M. v. Central Airlines, Inc., 372 U.S. 682, 685, 83 S. Ct. 956, 958, 10 L. Ed. 2d 67 (1963). The arbitration panel is a system adjustment board created by the parties to the collective bargaining agreement. See 45 U.S.C. § 184; Reed v. National Air Lines, Inc., 524 F.2d 456, 459 (5th Cir. 1975); de la Rosa Sanchez v. Eastern Airlines, Inc., 574 F.2d 29, 31 (1st Cir. 1978). A court may overturn the decision of an airline system adjustment board only on the basis of one of the grounds listed in 45 U.S.C. § 153 First (q).6 See Singer v. Flying Tiger Line, Inc., 652 F.2d 1349, 1355-56 (9th Cir. 1981); Northwest Airlines, Inc. v. Air Line Pilots Association International, 530 F.2d 1048, 1050 & n.9 (D.C.Cir.), cert. denied, 426 U.S. 942, 96 S. Ct. 2663, 49 L. Ed. 2d 394 (1976).

The exceedingly narrow scope of judicial review of labor arbitration decisions is tailored to suit the vital role that the arbitrator plays in the scheme of federal labor law. Not only is the arbitrator himself a linchpin of the ongoing collective bargaining relationship, the expeditiousness and the finality of the arbitration process serve to defuse the chronic crises that inhere in the labor setting and thereby prevent these crises from developing into labor unrest. See United Steelworkers v. Warrior & Gulf Navigation Co., 363 U.S. 574, 578-81, 80 S. Ct. 1347, 1350-52, 4 L. Ed. 2d 1409 (1960). To the extent that the courts intrude into this scheme, they detract both from the central role of the arbitrator and the palliative effect of the arbitration process. See United Steelworkers v. Enterprise Wheel & Car Corp., 363 U.S. 593, 598-99, 80 S. Ct. 1358, 1361-62, 4 L. Ed. 2d 1424 (1960).

In recognition of the limited judicial role in the arbitration process, courts have typically confined their scrutiny of awards to the broad contours of procedural fairness and arbitral impartiality. See, e.g., 45 U.S.C. § 153 First (q); Hines v. Anchor Motor Freight, Inc., 424 U.S. 554, 96 S. Ct. 1048, 47 L. Ed. 2d 231 (1976); Sam Kane Packing Co. v. Amalgamated Meat Cutters, 477 F.2d 1128 (5th Cir.), cert. denied, 414 U.S. 1001, 94 S. Ct. 355, 38 L. Ed. 2d 237 (1973); Bieski v. Eastern Automobile Forwarding Co., 396 F.2d 32 (3d Cir. 1968). Cf. United States Arbitration Act, 9 U.S.C. § 10 (commercial arbitration awards can be vacated, inter alia, for corruption or fraud, evident partiality of the arbitrator, and prejudicial misbehavior of the arbitrator).7 It is thus firmly established that courts will not review the substance of a labor arbitration award for ordinary error and that courts will not vacate an award because a judge might have reached a different result. See Safeway Stores v. American Bakery Workers, Local 111, 390 F.2d 79, 82-83 (5th Cir. 1968); Francesco's B., Inc. v. Hotel Employees Union, Local 28, 659 F.2d 1383, 1388-89 (9th Cir. 1981); R. Gorman, Basic Text on Labor Law 585-86 (1976). See also S.Rep.No.1201, 89th Cong., 2d Sess. 3 (1966), reprinted in 1966 U.S.Code Cong. & Ad.News 2285, 2287 (Senate Labor Committee rejected version of Railway Labor Act that would have permitted courts to vacate arbitral awards on grounds of "arbitrariness or capriciousness").

The substantive grounds for vacating labor arbitral awards that do exist are extremely narrow. In the railway labor field, 45 U.S.C. § 153 First (q) provides that an arbitral award may be vacated for failure "to conform, or confine itself, to matters within the scope of the division's jurisdiction." See also 9 U.S.C. § 10 (commercial arbitration award can be vacated when arbitration panel exceeds its jurisdiction). The courts have determined that this provision of section 153 is, in effect, a statutory codification of certain substantive grounds that would justify the vacation of an arbitral award in other areas of labor law. See Brotherhood of Railroad Trainmen v. Central of Georgia Ry., 415 F.2d 403, 410 (5th Cir. 1969), cert. denied, 396 U.S. 1008, 90 S. Ct. 564, 24 L. Ed. 2d 500 (1970). As exposited by the courts, there appear to be three interrelated grounds for such substantive review of arbitral awards:

(1) whether the award is irrational, see, e.g., Gunther v. San Diego & Arizona E. Ry., 382 U.S. 257, 261, 86 S. Ct. 368, 370, 15 L. Ed. 2d 308 (1965) ("wholly baseless and completely without reason"); Safeway Stores v. American Bakery Workers, Local 111, 390 F.2d at 82 ("if ... no judge, or group of judges, could ever conceivably have made such a ruling"); S.Rep.No.1201, supra, at 3, reprinted in 1966 U.S.Code Cong. & Ad.News, at 2287 ("actually and indisputably without foundation in reason or fact");

(2) whether the award draws its essence from the letter or purpose of the collective bargaining agreement, United Steelworkers v. Enterprise Wheel & Car Corp., 363 U.S. at 597, 80 S.Ct. at 1361; see Brotherhood of Railroad Trainmen v. Central of Georgia Ry., 415 F.2d at 412 (arbitrator's award "must have a basis that is at least rationally inferable, if not obviously drawn, from the letter or purpose of the collective bargaining agreement"); St. Antoine, Judicial Review of Labor Arbitration Awards: A Second Look at Enterprise Wheel and its Progeny, 75 Mich.L.Rev. 1137, 1147 (1977); and

(3) whether the arbitrator conformed to a specific contractual limitation upon his authority, see, e.g., Magnavox Co. v. International Union of Electrical Workers, 410 F.2d 388, 389 (6th Cir. 1969); Torrington Co. v. Metal Products Workers Union Local 1645, 362 F.2d 677, 680 (2d Cir. 1966); Textile Workers Union v. American Thread Co., 291 F.2d 894, 899-900 (4th Cir. 1961).

Although these interrelated grounds for substantive review share a basic concern that the arbitrator perform his contractually mandated role in a conscientious and responsible fashion,8 the third ground for review, that based upon specific contractual limitations, will not be equally applicable to every contract. See St. Antoine, supra, at 1142. Given the free play of the collective bargaining process, the parties to the contract could expressly grant the arbitrator power virtually to rewrite portions of the agreement, or expressly confine his authority within extremely narrow bounds.9 See R. Gorman, supra, at 586-93. As a practical matter, the most prevalent modification of arbitral authority is a contractual clause prohibiting the arbitrator from "adding to, subtracting from, or modifying the agreement in any way." See W. R. Grace & Co. v. Local Union No. 759, United Rubber Workers, 652 F.2d 1248, 1254 (5th Cir. 1981) (citing 2 BNA, Negotiations and Contracts P 51:281), cert. granted, --- U.S. ----, 102 S. Ct. 3481, 72 L.Ed.2d --- (1982).10

The collective bargaining agreement at issue in this case contains no such express constraint on the authority of the arbitrator to interpret the agreement.11 See also Syufy Enterprises v. Northern California State Association of IATSE Locals, 631 F.2d 124, 126 n.1 (9th Cir. 1980), cert. denied, 451 U.S. 983, 101 S. Ct. 2314, 68 L. Ed. 2d 839 (1981); Federated Employers of Nevada, Inc. v. Teamsters, Local 631, 600 F.2d 1263, 1264-65 (9th Cir. 1979); I.A.M., District No. 8 v. Campbell Soup Co., 406 F.2d 1223, 1226-27 (7th Cir.), cert. denied, 396 U.S. 820, 90 S. Ct. 57, 24 L. Ed. 2d 70 (1969); Truck Drivers Local Union No. 100 v. Quick-Freeze Cold Storage, Inc., 375 F. Supp. 725, 729 (S.D.Ohio 1974). Also, neither party suggests that the award is irrational. Therefore, the only substantive ground of review relevant to this case is whether the award draws its essence from the collective bargaining agreement.12

In this case, the superficially clear and unambiguous terms of the collective bargaining agreement entitled the three pilots to enhanced retirement benefits. The arbitrators went behind the contractual language to reach the opposite result based upon the panel's perception of the true intent of the parties to the collective bargaining agreement.

Appellees do not argue that the arbitrators were factually incorrect in their finding that the true intent of the parties was to exclude the pilots from supplemental benefits. Indeed, such an argument could hardly prevail in this court. See Safeway Stores v. American Bakery Workers, Local 111, 390 F.2d at 83-84.13 Rather, appellees contend that arbitrators may not go beyond the express terms of the collective bargaining agreement unless those terms evince a facial ambiguity. Phrased another way, appellees argue that unless the arbitrator adheres to the facially unambiguous language of the collective bargaining agreement, the arbitrator's award does not draw its essence from the collective bargaining agreement.14

In order to evaluate appellees' argument, it is necessary to examine the "essence" test set out by the Supreme Court in Enterprise Wheel. In that case, the Court stated:

(A)n arbitrator is confined to interpretation and application of the collective bargaining agreement; he does not sit to dispense his own brand of industrial justice. He may of course look for guidance from many sources, yet his award is legitimate only so long as it draws its essence from the collective bargaining agreement. When the arbitrator's words manifest an infidelity to this obligation, courts have no choice but to refuse enforcement of the award.

363 U.S. at 597, 80 S. Ct. at 1361. The Court suggested by way of example that an award "based solely upon the arbitrator's view of the requirements of enacted legislation" would fail to draw its essence from the contract. Id.

The interdiction contained in Enterprise Wheel has been invoked in a number of contexts. For example, in W. R. Grace & Co. v. Local Union No. 759, United Rubber Workers, 652 F.2d at 1255, the former fifth circuit determined that an arbitrator exceeded his jurisdiction by basing his award solely upon his perception of the equities of the situation without even referring to the collective bargaining agreement. In Detroit Coil Co. v. I.A.M., Lodge 82, 594 F.2d 575, 581 (6th Cir.), cert. denied, 444 U.S. 840, 100 S. Ct. 79, 62 L. Ed. 2d 52 (1979), the court vacated the award of an arbitrator who refused to apply a clear contractual time limit upon the filing of grievances because, inter alia, application of the clause might hurt the good relations that existed between the employer and the union. Additionally, in Textile Workers Union v. American Thread Co., 291 F.2d at 900-01, the court vacated an award that ignored the collective bargaining agreement and took as authority an unrelated arbitral decision.

These cases fit into a common pattern in which the arbitrator decides a matter according to a standard that reflects neither the language of the collective bargaining agreement nor the intent of the parties as embodied in the agreement. He thereby dispenses his own brand of industrial justice rather than the brand chosen by the parties that he was commissioned to dispense. Cf. St. Antoine, supra, at 1142 (arbitrator is official reader of collective bargaining agreement, so scope of judicial review should be determined by particular collective bargaining agreement involved).

It is immediately evident that the award in this case does not fit into the typical pattern of awards that fail the "essence" test. In this case, the arbitrators are not faulted for disregarding the intent of the parties to the collective bargaining agreement and thereby dispensing their "own brand of industrial justice." Rather, they are faulted for taking the original intent of the parties so seriously that they went behind ostensibly unambiguous language in the contract15 to determine precisely what the original intent was. We cannot conclude that such an award fails to draw its essence from the letter or purpose of the collective bargaining agreement.

In construing any contract, including a collective bargaining agreement, determining the intent of the parties is the essential inquiry. See Ludwig Honold Manufacturing Co. v. Fletcher, 405 F.2d 1123, 1131 (3d Cir. 1969). Although that intent will generally be discernible from the express words of a collective bargaining agreement, see Torrington Co. v. Metal Products Workers Union Local 1645, 362 F.2d at 681, we cannot always be certain that this is so. As stated by the Supreme Court, the collective bargaining agreement "is more than a contract; it is a generalized code to govern a myriad of cases which the draftsmen cannot wholly anticipate." United Steelworkers v. Warrior & Gulf Navigation Co., 363 U.S. at 578, 80 S.Ct. at 1350.16 Accordingly, absent some express restriction upon the arbitrator's authority, the arbitrator is not limited to the bare words of the agreement and common law rules for the interpretation of private contracts. Gunther v. San Diego & Arizona E. Ry., 382 U.S. at 261, 86 S.Ct. at 370. See St. Antoine, supra, at 1147.

An arbitrator does not violate his duty to draw the essence of his award from the letter or purpose of the collective bargaining agreement when he relies upon any of several aids to construe the intent of the parties in addition to the express terms of the contract. These extrinsic aids include the past practice of the parties, see, e.g., United Steelworkers v. Warrior & Gulf Navigation Co., 363 U.S. at 581-82, 80 S.Ct. at 1352-53; Boise Cascade Corp. v. United Steelworkers, Local Union No. 7001, 588 F.2d 127, 129-30 (5th Cir.), cert. denied, 444 U.S. 830, 100 S. Ct. 57, 62 L. Ed. 2d 38 (1979), bargaining history, see, e.g., Francesco's B., Inc. v. Hotel Employees, Local 28, 659 F.2d at 1389; U.A.W. v. White Motor Corp., 505 F.2d 1193, 1198-99 (8th Cir. 1974), cert. denied, 421 U.S. 921, 95 S. Ct. 1588, 43 L. Ed. 2d 789 (1975), relevant legislation to the extent that it is probative of the "sense of the agreement," see, e.g., United Steelworkers v. Enterprise Wheel & Car Corp., 363 U.S. at 597-98, 80 S.Ct. at 1361; Marble Products Co. v. Local 155, United Stone Workers, 335 F.2d 468, 472 (5th Cir. 1964), and industrial efficiency considerations "insofar as the collective bargaining agreement permits," see, e.g., United Steelworkers v. Warrior & Gulf Navigation Co., 363 U.S. at 582, 80 S.Ct. at 1352; Truck Drivers Local Union No. 100 v. Quick-Freeze Cold Storage, Inc., 375 F. Supp. at 730.

In this case, the arbitration clause of the collective bargaining agreement contained no express limitations upon the authority of the arbitrators to interpret the agreement. The arbitrators relied upon probative evidence of bargaining history to determine that the parties did not intend that employees in appellees' position would receive enhanced retirement benefits. Perhaps this is not the result that a judge, applying ordinary principles of contract construction, would have reached. In light of our narrow standard of review of arbitral awards, however, that fact is totally irrelevant. Safeway Stores v. American Bakery Workers, Local 111, 390 F.2d at 83-84. The arbitration panel, composed of designees of both Eastern and ALPA, reached that result on the basis of a construction of the collective bargaining agreement that comported with the essence of the agreement. It was the responsibility of the district court to affirm the award.

REVERSED AND REMANDED.