Today looks rough: weather pushes the average chance of arriving 15+ min late to 51%, against 35% on a calm day. Safest: UA 2028 at 19:20, 42%.

Safest bet today UA 2028 DEN 19:20 → ONT 20:42 · 42% chance 15+ min late · usually 75% on time Riskiest WN 1663 DEN 21:10 → ONT 22:30 · 55% chance 15+ min late · usually 35% on time

Weather 51% average chance a nonstop arrives 15+ min late; 35% for the same flights on a calm-weather day

Every nonstop today

12-month record →

Ranked by the chance of arriving 15+ minutes late, with each flight’s on-time record over Aug 2025 – Jul 2026 beside it. Times are local. Pick a flight for its forecast. Click a column to sort. 6 flights that already left today are not shown.


UA 2028 United Flight history →	DEN 19:20	ONT 20:42	42%	12%	0.2%	75%worse than usual
WN 1712 Southwest	DEN 18:30	ONT 19:58	51%	9%	0.2%	no record
WN 2949 Southwest Flight history →	DEN 18:30	ONT 19:55	52%	9%	0.2%	40%
F9 1261 Frontier Flight history →	DEN 22:29	ONT 23:50	52%	15%	0.4%	81%worse than usual
WN 1713 Southwest	DEN 20:52	ONT 22:20	54%	11%	0.2%	no record
WN 1663 Southwest Flight history →	DEN 21:10	ONT 22:30	55%	11%	0.2%	35%

How these are worked out. Each flight’s odds are our forecast for that day; flights of airlines we don’t forecast yet use their 12-month record and are marked. Makes the connection: the first flight’s 12-month lateness curve, scaled so its chance of arriving 15+ min late matches the day’s forecast, at the layover minus the 45-minute minimum (90 on separate tickets). Arrives on time: first flight not cancelled × connection made × second flight not cancelled × second flight within 15 minutes, each from the day’s forecast.

About this data: forecast odds from our model for Sun, Oct 4 (newest published update); 12-month records from US DOT on-time data, Aug 2025 – Jul 2026, all US airlines; regional flights count under the airline that sells them. JSON