Today: WN 3749 at 06:55 is the safest bet, 4% chance of being 15+ min late; the others run 5–27%.

Safest bet today WN 3749 SLC 06:55 → MDW 10:55 · 4% chance 15+ min late · usually 100% on time Riskiest WN 3750 SLC 14:05 → MDW 18:05 · 27% chance 15+ min late · usually 57% on time

Against a calm day 16% average chance a nonstop arrives 15+ min late; 14% 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 3749 Southwest Flight history →	SLC 06:55	MDW 10:55	4%	1%	0.1%	100%
WN 549 Southwest	SLC 07:11	MDW 11:18	5%	1%	0.1%	no record
WN 3885 Southwest	SLC 13:28	MDW 17:36	25%	4%	0.5%	no record
WN 3750 Southwest Flight history →	SLC 14:05	MDW 18:05	27%	5%	0.5%	57%

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