Today: WN 551 at 09:15 is the safest bet, 9% chance of being 15+ min late; evening flights run 27–30%.

Safest bet today WN 551 DAL 09:15 → COS 10:22 · 9% chance 15+ min late Riskiest WN 4786 DAL 19:20 → COS 20:15 · 30% chance 15+ min late · usually 45% on time

Against a calm day 20% average chance a nonstop arrives 15+ min late; 21% 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.


WN 551 Southwest	DAL 09:15	COS 10:22	9%	2%	0.2%	no record
WN 3257 Southwest Flight history →	DAL 11:05	COS 12:00	15%	3%	0.1%	71%
WN 1245 Southwest	DAL 20:30	COS 21:35	27%	6%	0.5%	no record
WN 4786 Southwest Flight history →	DAL 19:20	COS 20:15	30%	6%	0.5%	45%

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 Mon, Oct 5 (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