Today: UA 1738 at 22:20 is the safest bet, 17% chance of being 15+ min late; the others run 17–45%.

Safest bet today UA 1738 IAD 22:20 → ORD 23:31 · 17% chance 15+ min late · usually 80% on time Riskiest UA 2497 IAD 17:42 → ORD 18:50 · 45% chance 15+ min late · usually 48% on time

Against a calm day 27% average chance a nonstop arrives 15+ min late; 25% 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. 4 flights that already left today are not shown.


UA 1738 United Flight history →	IAD 22:20	ORD 23:31	17%	6%	0.3%	80%
UA 421 United	IAD 22:31	ORD 23:47	17%	6%	0.3%	no record
UA 2331 United Flight history →	IAD 13:15	ORD 14:29	22%	7%	0.2%	81%
UA 1393 United Flight history →	IAD 15:39	ORD 17:02	30%	9%	0.3%	64%
UA 1703 United	IAD 15:44	ORD 16:46	33%	9%	0.3%	no record
UA 2497 United Flight history →	IAD 17:42	ORD 18:50	45%	9%	0.2%	48%

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