May 2026 · US Department of Transportation filings
Airlines blame the weather.
The filings say otherwise.
Every large US airline reports its delays to the federal government each month, including what caused them. Across 442,954 domestic flights in May 2026, 74.5% of all delay minutes traced back to the airlines themselves, against 3.9% for weather. These are the carriers' own filings, not our estimates, and every figure below links to the source.
74.5%
of delay minutes are the airline's own doing
3.9%
of delay minutes are weather
22%
of flights arrived over 15 minutes late
Ranked by how often they arrive late
Southwest Airlines ran latest at 27.5%; Alaska Airlines was most reliable at 16.7%. The last column is the one airlines do not advertise.
| Airline | Flights | Over 15 min late | Cancelled | Avg delay | Airline's own fault | Weather |
|---|---|---|---|---|---|---|
| Southwest AirlinesWN | 120,646 | 27.5% | 0.4% | 15.6 min | 81.1% | 2.3% |
| Frontier AirlinesF9 | 18,423 | 23.2% | 0.5% | 18.8 min | 75.9% | 2.3% |
| American AirlinesAA | 88,740 | 23% | 1.5% | 20 min | 79% | 7.1% |
| United AirlinesUA | 74,200 | 19.9% | 0.4% | 14.1 min | 62.1% | 3.9% |
| JetBlue AirwaysB6 | 19,806 | 18.5% | 0.2% | 12.7 min | 69.2% | 2.6% |
| Delta Air LinesDL | 91,955 | 17.5% | 1.2% | 12.2 min | 73.7% | 3.2% |
| Alaska AirlinesAS | 29,184 | 16.7% | 0.7% | 9.1 min | 70.5% | 4.2% |
Where the delay minutes actually go
Each bar is one carrier's delay minutes split by the cause it filed. Red and orange are the airline's own operation; blue and grey are outside its control.
- Carrier — crew, maintenance, fuelling
- Late inbound aircraft
- Air traffic system
- Weather
Down to the route
A carrier-wide figure hides a lot: the same airline can run 12% late on one city pair and 40% on another. We publish the same breakdown for every busy route in the dataset, each direction measured separately.
Browse route delay recordsMethodology, and what this does not cover
- Source
- The US DOT Bureau of Transportation Statistics Reporting Carrier On-Time Performance database, month 2026-05, retrieved 2026-07-28. Nothing here is modelled, estimated or crowd-sourced. Airlines file these numbers themselves under federal requirement.
- “Airline's own fault” is our grouping, not a BTS field
- BTS reports five causes separately. We add carrier delay to late-inbound-aircraft delay, on the grounds that an aircraft arriving late from its previous leg is the same airline's earlier delay travelling with the plane. Both components are shown separately above so you can reject that grouping and use the raw carrier figure instead. It changes the ranking: Delta has the highest raw carrier share but among the lowest knock-on share.
- Minimum sample
- Route and airport figures are withheld below 300 flights in the period. A thin route produces dramatic percentages from a handful of bad days — one route showed 62% late off 106 flights, which is noise, not a finding. Carrier totals need no threshold; the smallest here files over 18,000 flights.
- Domestic US only — no Mexico, no Europe
- 14 CFR part 234 requires reporting from US carriers above 0.5% of domestic scheduled-service passenger revenue, and it covers domestic service. We checked: across 442,954 flights, no Mexican airport appears at all. So this says nothing about any cross-border route, and nothing about Volaris, Viva Aerobus or Aeroméxico. Mexican carrier data has to come from AFAC, which is a separate source we have not published.
- One month, not a trend
- This is a single reporting month and carries that month's seasonality. It is a snapshot, and we would rather label it as one than present a single month as a pattern.
- Reproduce it
- The figures come from the bulk file BTS publishes at a stable URL, aggregated by a script in this repository. Anyone can download the same file and check every number on this page.
Figures cover May 2026, a single reporting month, from the US DOT Bureau of Transportation Statistics On-Time Performance database. Retrieved 2026-07-28. Reporting under 14 CFR part 234 covers domestic US scheduled service only, so no international route appears — including anything to or from Mexico.
Delayed on one of these airlines?
Whether the cause was the airline's own matters legally, not just reputationally: Mexican law owes compensation only where the delay is attributable to the carrier, and US law owes a refund past a threshold that differs for domestic and international trips. Our checker works out which applies and cites the provision.
Check what you are owed