Monday, October 5 · our forecast odds · issued Sun 8:00 PM ET · 3 nonstops

Tomorrow: WN 3978 at 08:10 is the safest bet, 6% chance of being 15+ min late; the others run 6–20%.

Safest bet that day WN 3978 STL 08:10 → SAT 10:15 · 6% chance 15+ min late · usually 73% on time Riskiest WN 3979 STL 22:15 → SAT 00:25 · 20% chance 15+ min late · usually 65% on time

Against a calm day 11% average chance a nonstop arrives 15+ min late; 9% for the same flights on a calm-weather day

Every nonstop on Mon, Oct 5

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 3978 Southwest Flight history →	STL 08:10	SAT 10:15	6%	1%	0.1%	73%
WN 4922 Southwest	STL 08:30	SAT 10:53	6%	1%	0.4%	no record
WN 3979 Southwest Flight history →	STL 22:15	SAT 00:25	20%	4%	0.5%	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