New Data Shows Delta’s Reliability Fell Apart In July — 4,626 Flights Canceled, Nearly 3X Southwest

Delta fell to fourth place for on-time performance in July. The bigger deal is that they cancelled nearly 3% of their flights for the month – over 4,600 cancellations – according to aviation analytics company Cirium. That’s worse than United and American and even about 2.6 times as many cancellations as Southwest. Weather was involved, but what Delta has shown is that they’ve become the worst U.S. airline at recovering from major events except perhaps for JetBlue. They’ve correctly blamed pilot scheduling as a challenge, but it’s also very much on their own management not just for agreeing to provisions in their own pilot contract that their IT systems can’t keep up with but running an operation too short of cockpit crew. Senior executives warned in the spring that their issues would continue through summer, and they have – and they’ve gotten worse. Southwest, meanwhile, improved its on-time performance three from June, but remained an abysmal 67.19% which is 6.6 points below its first-half average for 2026. They aren’t cancelling many flights (just 1%), they’re operating their schedule, but running late about a third of the time. Charging for checked bags, filling the cabin with carry-ons, means boarding and deplaning takes longer and more bags need to be gate checked – that has hampered them somewhat all year, but July was significantly worse. During Southwest’s second quarter earnings call, they acknowledged this issue slowing their ability to turn aircraft quickly, and they’re planning schedule changes to improve reliability later this year. Data from Cirium shows airline on-time performance for July 2026: Rank Airline On-time Completion Cancels 1 WestJet 83.90% 99.50% 109 2 Alaska 76.20% 99% 528 3 United 75.40% 97.60% 3,877 4 Delta 75% 97.20% 4,626 5 American 72% 97.30% 5,669 6 Allegiant 70% 99.50% 67 7 AirCanada 68.50% 94.90% 1,867 8 Southwest 67.20% 98.90% 1,388 9 Frontier 65.50% 97.60% 532 10 JetBlue 62.20% 91.70% 2,597 Delta cancelled about 3.3 times as many flights as Southwest despite scheduling just 28% more flights. If Delta had matched its 2025 completion factor, they would have cancelled 2,519 fewer flights in July. There were New York storms July 16-18 and a broader Northeast weather event July 21–22, and another New York event July 26-29. That hammered United, too, which has a similar New York presence and more difficult setup at Newark. Atlanta saw severe weather on July 24–25. The major issue, though, is how airlines recover from these events – while Delta problems tend to cascade. Cirium’s North America aggregate on-time performance fell from 79.30% in May to 75.54% in June and 71.58% in July. JetBlue of course had a true meltdown in July even considering their operational performance frequently lags the industry. A 91.7% completion factor – cancelling over 8% of flights – is mind-boggling. Weather hit the Northeast several times but they didn’t just get hit, they absolutely cratered in response. Topics on this page