Today: WN 3151 at 11:05 is the safest bet, 12% chance of being 15+ min late; evening flights run 30–35%.

Safest bet today WN 3151 SJC 11:05 → ONT 12:20 · 12% chance 15+ min late · usually 88% on time Riskiest WN 2583 SJC 16:45 → ONT 18:05 · 35% chance 15+ min late

Against a calm day 24% average chance a nonstop arrives 15+ min late; 20% 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. 2 flights that already left today are not shown.


WN 3151 Southwest Flight history →	SJC 11:05	ONT 12:20	12%	3%	0.2%	88%
WN 3826 Southwest	SJC 12:20	ONT 13:50	14%	4%	0.2%	no record
WN 1341 Southwest	SJC 15:20	ONT 16:50	21%	7%	0.2%	no record
WN 1198 Southwest	SJC 21:25	ONT 22:54	30%	16%	0.5%	no record
WN 3692 Southwest Flight history →	SJC 21:55	ONT 23:15	33%	16%	0.4%	45%
WN 2583 Southwest	SJC 16:45	ONT 18:05	35%	9%	0.2%	no record

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 Sun, Oct 4 (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