The impact of recent US Airline mergers on competition and pricing

The impact of recent US Airline mergers on competition and pricing

Economics

Karl Bichmann

2025

I study the Delta–Northwest (2009) and American–US Airways (2013) mergers using a route–quarter panel from DB1B. The focus is nonstop city pairs. I run a transparent difference-in-differences design that compares pre-merger overlap routes with non-overlap routes inside a linked-only sample. Regressions are passenger-weighted, include route and quarter fixed effects, and cluster standard errors by route. I also look at two predefined subsets: markets where the merging brands jointly held at least 50 to 70 percent of pre-merger passengers, and the top decile of routes by pre-merger passengers. In the baseline, Delta–Northwest overlap routes show fares about 2 percent lower with passenger volumes roughly unchanged. For American–US Airways, fares are flat to slightly lower and passengers are about 4 to 5 percent higher. In concentrated Delta–Northwest markets, fare effects turn positive and rise with the threshold, about +4, +7, and +9 percent at 50, 60, and 70 percent, with passenger declines at the higher cutoffs. For American–US Airways the pattern differs: fares fall by about 6.0, 6.7, and 5.6 percent, while passengers rise by about 11.8, 13.5, and 9.5 percent across the same thresholds. On the busiest trunk routes, Delta–Northwest shows a small fare decrease of roughly 2.6 percent with volumes flat, and American–US Airways shows no meaningful fare change paired with about 4.3 percent higher passengers. Read through standard unilateral-effects logic, the Delta–Northwest severe-subset results are consistent with internalization of undercutting where the two brands were closest substitutes before the merger. The American–US Airways results and the busiest-route findings point to network and schedule efficiencies that expand volumes without higher posted fares. Overall, there is no evidence of broad fare increases on nonstop overlap routes; concerns are most plausible in already concentrated Delta–Northwest markets, while efficiency gains appear more salient on trunk corridors.

Airlines; Mergers;