Today: WN 4048 at 05:50 is the safest bet, 4% chance of being 15+ min late; evening flights run 27–28%.

Safest bet today WN 4048 TPA 05:50 → STL 07:10 · 4% chance 15+ min late · usually 98% on time Riskiest WN 4964 TPA 21:10 → STL 22:40 · 28% chance 15+ min late · usually 65% on time

Against a calm day 17% average chance a nonstop arrives 15+ min late; 11% 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 4048 Southwest Flight history →	TPA 05:50	STL 07:10	4%	1%	0.2%	98%
WN 4197 Southwest	TPA 06:15	STL 07:44	4%	1%	0.2%	no record
WN 4049 Southwest Flight history →	TPA 10:15	STL 11:40	13%	3%	0.2%	81%
WN 3345 Southwest	TPA 12:30	STL 13:59	24%	5%	0.2%	no record
WN 1123 Southwest	TPA 21:45	STL 23:15	27%	9%	0.7%	no record
WN 4964 Southwest Flight history →	TPA 21:10	STL 22:40	28%	9%	0.7%	65%

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