Today: WN 1421 at 13:50 is the safest bet, 33% chance of being 15+ min late; evening flights run 47–55%.

Safest bet today WN 1421 DEN 13:50 → DAL 16:55 · 33% chance 15+ min late Riskiest WN 1578 DEN 19:10 → DAL 22:09 · 55% chance 15+ min late

Against a calm day 47% average chance a nonstop arrives 15+ min late; 42% 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. 9 flights that already left today are not shown.


WN 1421 Southwest	DEN 13:50	DAL 16:55	33%	5%	0.4%	no record
WN 2399 Southwest	DEN 13:49	DAL 16:48	37%	5%	0.4%	no record
WN 3668 Southwest	DEN 15:08	DAL 18:07	46%	8%	0.5%	no record
WN 1521 Southwest Flight history →	DEN 18:25	DAL 21:35	47%	11%	0.4%	39%
WN 2511 Southwest	DEN 15:40	DAL 18:40	47%	8%	0.4%	no record
WN 1523 Southwest Flight history →	DEN 20:25	DAL 23:30	48%	14%	0.3%	41%
WN 553 Southwest	DEN 19:15	DAL 22:15	49%	12%	0.4%	no record
WN 1579 Southwest	DEN 20:10	DAL 23:10	54%	13%	0.3%	no record
WN 2956 Southwest	DEN 17:08	DAL 20:07	54%	11%	0.4%	no record
WN 1578 Southwest	DEN 19:10	DAL 22:09	55%	13%	0.4%	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