Today looks rough: weather pushes the average chance of arriving 15+ min late to 54%, against 38% on a calm day. Safest: WN 3851 at 14:30, 48%.

Safest bet today WN 3851 LAS 14:30 → STL 19:45 · 48% chance 15+ min late · usually 56% on time Riskiest WN 3863 LAS 18:10 → STL 23:22 · 60% chance 15+ min late

Weather 54% average chance a nonstop arrives 15+ min late; 38% 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. 7 flights that already left today are not shown.


WN 3851 Southwest Flight history →	LAS 14:30	STL 19:45	48%	11%	0.1%	56%
WN 2371 Southwest Flight history →	LAS 19:45	STL 00:55	49%	11%	0.1%	58%
WN 4890 Southwest	LAS 19:25	STL 00:38	53%	11%	0.1%	no record
WN 1397 Southwest	LAS 18:20	STL 23:40	58%	11%	0.1%	no record
WN 3863 Southwest	LAS 18:10	STL 23:22	60%	12%	0.1%	no record

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