Today looks rough: weather pushes the average chance of arriving 15+ min late to 45%, against 26% on a calm day. Safest: DL 4039 at 19:59, 35%.

Safest bet today DL 4039 SEA 19:59 → BZN 22:49 · 35% chance 15+ min late · usually 84% on time Riskiest AS 458 SEA 20:40 → BZN 23:19 · 58% chance 15+ min late · usually 67% on time

Weather 45% average chance a nonstop arrives 15+ min late; 26% 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. 1 flight that already left today is not shown.


DL 4039 Delta flown by SkyWest Flight history →	SEA 19:59	BZN 22:49	35%	7%	0.4%	84%worse than usual
DL 4104 Delta flown by SkyWest Flight history →	SEA 12:17	BZN 15:14	43%	14%	0.5%	84%worse than usual
AS 3498 Alaska flown by SkyWest Flight history →	SEA 15:35	BZN 18:18	45%	9%	0.4%	71%worse than usual
AS 458 Alaska Flight history →	SEA 20:40	BZN 23:19	58%	11%	0.5%	67%worse than usual

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