Friday, October 9 · typical odds for a Friday (too early for a weather forecast) · issued Sun 4:00 PM ET · 5 nonstops

Fri, Oct 9: WN 3239 at 05:25 is the safest bet, 3% chance of being 15+ min late; evening flights run 25–26%.

Safest bet that day WN 3239 BOS 05:25 → MDW 07:00 · 3% chance 15+ min late · usually 91% on time Riskiest WN 3911 BOS 18:45 → MDW 20:35 · 26% chance 15+ min late · usually 43% on time

Every nonstop on Fri, Oct 9

12-month record →

Ranked by the chance of arriving 15+ minutes late (typical odds: the weather this date has had in past years), 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 3239 Southwest Flight history →	BOS 05:25	MDW 07:00	3%	1%	0.6%	91%
WN 745 Southwest Flight history →	BOS 07:30	MDW 09:10	7%	1%	0.6%	91%
WN 746 Southwest Flight history →	BOS 13:10	MDW 14:45	18%	3%	0.6%	66%
WN 4106 Southwest Flight history →	BOS 16:45	MDW 18:35	25%	7%	0.6%	54%
WN 3911 Southwest Flight history →	BOS 18:45	MDW 20:35	26%	7%	0.6%	43%

How these are worked out. Each flight’s odds are our forecast for that day (typical odds until the weather forecast covers it); 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 Fri, Oct 9 (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