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 4122 at 07:35 is the safest bet, 5% chance of being 15+ min late; the others run 7–29%.

Safest bet that day WN 4122 MDW 07:35 → PHL 10:35 · 5% chance 15+ min late · usually 94% on time Riskiest WN 4263 MDW 18:55 → PHL 21:55 · 29% chance 15+ min late · usually 51% 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 4122 Southwest Flight history →	MDW 07:35	PHL 10:35	5%	1%	0.6%	94%
WN 4901 Southwest Flight history →	MDW 09:00	PHL 11:55	7%	2%	0.6%	96%
WN 4351 Southwest Flight history →	MDW 13:40	PHL 16:45	20%	5%	0.7%	57%
WN 4948 Southwest Flight history →	MDW 15:20	PHL 18:20	22%	6%	0.7%	60%
WN 4263 Southwest Flight history →	MDW 18:55	PHL 21:55	29%	7%	0.7%	51%

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