Scenario analysis / observed shares

Merger structure lab

Calculate a hypothetical concentration change from two published participant shares. This is an arithmetic screen, not a claim that a transaction exists or a legal conclusion.

Live scenarioDelta Air Lines+American Airlines

Delta HHI+623Post HHIWithheld

Eligible markets: 6; Observed firm-level shares
Observed periods: 18; Definition-matched snapshots
Complete HHI screens: 17; Baseline and post-merger HHI
Share observations: 136; Named, source-labeled rows

Scenario layer

Market, observed period, and two source-labeled participants can change.

Evidence layer

Published shares, baseline HHI, source status, confidence, and definition remain fixed.

Interpretation layer

Numeric conditions are screening inputs, never a standalone liability or outcome claim.

Observed-share scenario

Structure screen

Market profileObserved periodScenario party AScenario party B

Domestic airlinesUnited StatesAgency definedPassenger shares91%named share coverageDelta onlyHigh confidence

Transportation / 2026

Delta Air Lines + American Airlines

2 x 17.8% x 17.5% = 623 HHI points

Numeric condition crossedThe selected shares cross the merged-share path.

Baseline HHI: Withheld; Source record withheld
Delta HHI: +623; Exact 2ab arithmetic
Post-merger HHI: Withheld; Cannot be completed
Merged share: 35.3%; 17.8% + 17.5%

Participant geometryObserved shares, combined only for this scenario

Observed2026

Delta Air Lines17.8%American Airlines17.5%Southwest Airlines17%United Airlines16.7%Other airlines9%

CombinedScenario

Delta Air Lines + American Airlines35.3%Southwest Airlines17%United Airlines16.7%Other airlines9%

Delta Air Lines + American Airlines35.3%Southwest Airlines17%United Airlines16.7%Other airlines9%Alaska Airlines6.3%JetBlue Airways4.5%Frontier Airlines3.7%Spirit Airlines3.3%SkyWest Airlines2.6%Hawaiian Airlines1.6%

Guideline 1 numeric pathsOfficial reference

Evidence contractOpen market profile

The scenario inherits this published boundary

Product: Domestic scheduled airline passenger traffic
Geography: United States domestic itineraries
Measurement: Carrier share of domestic scheduled passengers
Denominator: Passengers reported in the BTS domestic market-share table for the 12 months ending February 2026

IncludedNamed carriers and the published aggregate Other category

ExcludedIndividual carriers inside Other are not separately identified

LimitationThe aggregate Other row prevents a complete firm-level distribution and therefore prevents a publishable HHI.

Reusable scenario packet

Carry the exact inputs into research

Antitrust Radar, Merger Structure Lab: Delta Air Lines + American Airlines in U.S. domestic airline passengers (2026); observed shares 17.8% and 17.5%; ΔHHI 623; baseline HHI withheld.

JSON CSV

Source custody

TranStats airline domestic market share March 2025-February 2026Bureau of Transportation Statistics 2023 Merger Guidelines, Guideline 1U.S. Department of Justice and Federal Trade Commission / December 18, 2023

01This tool combines two observed shares as a research scenario. It does not report an actual transaction, define a legal market, or predict an agency or court outcome.

02The calculation inherits the published agency defined boundary, United States domestic itineraries, measurement basis, denominator, and source limitations shown below.

03The baseline HHI is withheld, so the exact share-based delta does not establish a post-merger HHI or complete the HHI threshold path.

04Guideline 1 concentration arithmetic is one screening framework. The Merger Guidelines identify additional fact-specific theories, evidence, and rebuttal considerations.

The JSON and CSV packets preserve the selected shares, arithmetic, thresholds, evidence status, definition contract, sources, citation, and guardrails.