Friday, October 9 · typical odds for a Friday (too early for a weather forecast) · issued Sat 8:00 PM ET · 4 nonstops

Fri, Oct 9: WN 4879 at 06:35 is the safest bet, 2% chance of being 15+ min late; evening flights run 27–29%.

Safest bet that day WN 4879 SJC 06:35 → ONT 07:55 · 2% chance 15+ min late · usually 98% on time Riskiest WN 3692 SJC 20:15 → ONT 21:35 · 29% chance 15+ min late · usually 45% 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 4879 Southwest Flight history →	SJC 06:35	ONT 07:55	2%	1%	0.6%	98%
WN 3151 Southwest Flight history →	SJC 10:50	ONT 12:05	11%	5%	0.6%	88%
WN 3691 Southwest Flight history →	SJC 16:40	ONT 18:00	27%	10%	0.5%	50%
WN 3692 Southwest Flight history →	SJC 20:15	ONT 21:35	29%	13%	0.5%	45%

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