Antitrust Law Daily Wrap Up, ANTITRUST—D.D.C.: Delta and United’s renewed bid for summary judgment and interlocutory appeal falls short in ongoing airline antitrust MDL, (Sep 30, 2025)

By Martin A. Steinberg, J.D.

Consumers in a nationwide class action allege that major U.S. airlines, including American, Delta, Southwest, and United, conspired to restrict domestic flight capacity to fix ticket prices in violation of Section 1 of the Sherman Act.

The federal district court in the District of Columbia denied Delta Air Lines and United Airlines’ motions seeking reconsideration of the court’s earlier order denying summary judgment in the long-running antitrust MDL action. The court held that the airlines failed to identify any clear error, intervening change in law, or new evidence warranting reversal of its prior findings that genuine disputes of material fact remained regarding the alleged conspiracy to restrict capacity and raise fares. The court further rejected the defendants’ request for interlocutory appeal under 28 U.S.C. § 1292(b), concluding that the issues raised did not present a controlling question of law or substantial grounds for a difference of opinion. Emphasizing that reconsideration cannot serve as a vehicle for rearguing prior positions, the court reaffirmed that the plaintiffs had presented sufficient circumstantial and expert evidence to proceed to trial against the remaining airline defendants. Southwest and American had previously settled with the plaintiffs in May 2019 (In re Domestic Airline Travel Antitrust Litigation, No. 1:15-mc-01404-CKK (D.D.C. Sept. 29, 2025)).

Motion for interlocutory appeal. The court denied the defendants’ motion for interlocutory appeal by noting that reconsideration is not a vehicle for reargument. Delta and United’s submissions essentially revisited factual and legal contentions that had already been addressed, offering no basis to alter the court’s prior conclusions. The court reaffirmed that the plaintiffs’ case rests on an integrated evidentiary record, spanning executive statements, synchronized conduct, and expert economic findings, which raise genuine issues of material fact for trial regarding whether the airlines conspired to limit domestic capacity and inflate fares.

The court noted that such motions are disfavored and granted only in limited circumstances, specifically, when there is an intervening change in controlling law, new evidence previously unavailable, or a clear error of law or fact resulting in manifest injustice. Neither airline met that burden. Instead, the motions largely rehashed arguments that the court had already considered and rejected at the summary judgment stage.

Delta and United asserted that the court misapplied the summary judgment standard by crediting plaintiffs’ circumstantial evidence and failing to give proper weight to each defendant’s independent business justifications. The airlines argued that their conduct, public statements about capacity discipline, reductions in seat growth, and alignment with competitors’ output decisions, was consistent with legitimate economic strategy rather than collusion. The court rejected this framing, explaining that the court’s role at summary judgment is not to weigh the evidence but to determine whether genuine disputes of material fact exist. Because the plaintiffs’ expert and documentary evidence could support a reasonable inference of a concerted effort to limit capacity, summary judgment remained improper.

The court reviewed specific categories of evidence that the plaintiffs relied upon, including parallel announcements by airlines regarding capacity restraint, similar timing in route reductions, and repeated public assurances to investors that competitors would avoid aggressive capacity expansion. Plaintiffs’ expert analysis, which found statistically significant correlations in the airlines’ capacity decisions inconsistent with independent competition, was deemed admissible and probative. Delta and United contended that these communications were routine market updates and that the plaintiffs failed to exclude lawful explanations for the parallel behavior. The court disagreed, holding that “plus factors” such as inter-airline communications through trade associations, investor meetings, and analyst conferences could allow a factfinder to infer a tacit agreement to maintain fares through capacity discipline.

Delta also challenged the court’s reliance on internal communications referencing “capacity restraint” and “industry coordination,” arguing that these phrases were misinterpreted. The court found that such evidence, while subject to competing interpretations, was for a jury to evaluate. United similarly claimed the court erred in crediting plaintiffs’ expert testimony, asserting that the model failed to control for external economic variables and industry trends. These arguments pertained to weight, not admissibility, and the court reaffirmed that the plaintiffs’ expert presented a coherent economic theory consistent with antitrust precedent, which permits proof of conspiracy by circumstantial means.

The court further rejected the airlines’ attempt to invoke prior rulings as controlling precedent. Their reliance on earlier decisions in unrelated industries did not demonstrate clear error. Nor did they present any new facts that undermined the earlier determination that plaintiffs had marshaled sufficient statistical, documentary, and testimonial evidence to allow a reasonable jury to infer unlawful coordination under Section 1 of the Sherman Act.

Motion for reconsideration. The court concluded that the defendants failed to establish any basis for disturbing its earlier ruling, which denied the defendants’ motions for summary judgment. The motion sought only to revisit factual disputes and reframe arguments the court had already addressed in its comprehensive summary judgment opinion. The decision left intact the finding that plaintiffs’ evidence of coordinated capacity restraint was sufficient to proceed to trial under Section 1 of the Sherman Act.

The airlines contended that the court’s prior denial of summary judgment misapplied the legal standards governing Section 1 of the Sherman Act, improperly credited plaintiffs’ circumstantial evidence, and failed to recognize that the record established only lawful, independent business conduct. The court rejected each contention, emphasizing that defendants had identified no intervening change in controlling law, new evidence, or clear error warranting revision.

The court recognized that the plaintiffs had introduced substantial circumstantial and expert evidence, including coordinated public statements, contemporaneous capacity decisions, and investor communications, which raised genuine disputes of material fact concerning whether the defendants had conspired to restrict capacity and maintain higher fares. The court reiterated that antitrust conspiracies are often proven through indirect evidence and that evaluating competing interpretations of that evidence is a task for the jury, not for summary judgment.

Delta and United’s arguments, the court observed, merely repackaged positions previously rejected, such as their claim that parallel conduct and “capacity discipline” statements were consistent with legitimate business rationales. The existence of plausible alternative explanations does not preclude a finding of conspiracy where sufficient “plus factors,” including inter-firm communications and synchronized decision-making, supported an inference of agreement.

Motion to file amicus brief. In the final portion of the opinion, the court addressed a motion for leave to file an amicus curiae brief submitted in connection with Delta’s and United’s reconsideration and interlocutory appeal requests. The proposed amicus, a trade association representing airline industry interests, sought to offer what it characterized as context on capacity-management practices and economic policy implications relevant to the antitrust claims.

The court denied the motion, finding that the proposed amicus submission would not aid the court’s resolution of the pending motions. Amicus participation at the district court level is discretionary and appropriate only when the party offers distinct legal arguments or specialized expertise unavailable from the existing record. Here, the court determined that the proposed filing merely echoed positions already advanced by the defendants, particularly regarding lawful business justifications for “capacity discipline” and the interpretation of parallel conduct evidence. Because the defendants had fully briefed those issues, an additional amicus perspective would be duplicative rather than helpful.

The court further noted that amicus briefs are generally reserved for matters presenting broader public policy questions or novel constitutional issues, neither of which was implicated in the reconsideration or interlocutory appeal motions. The dispute before the court concerned the sufficiency of the evidentiary record, not abstract legal principles or policy analysis. Allowing the proposed brief, the court reasoned, would only add redundancy and delay.

The Case is No. 1:15-mc-01404-CKK.

Judge: Kollar-Kotelly, C.

Attorneys: Kit A. Pierson (Cohen Milstein Sellers & Toll PLLC) For William Youmans. Michael S. Mitchell (Boies, Schiller & Flexner Llp) for Delta Airlines, Inc.

Companies: Delta Airlines, Inc.

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