Today looks rough: weather pushes the average chance of arriving 15+ min late to 60%, against 31% on a calm day. Safest: WN 3955 at 21:20, 51%.

Safest bet today WN 3955 SMF 21:20 → ONT 22:56 · 51% chance 15+ min late Riskiest WN 480 SMF 19:00 → ONT 20:20 · 67% chance 15+ min late · usually 75% on time

Weather 60% average chance a nonstop arrives 15+ min late; 31% 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. 7 flights that already left today are not shown.


WN 3955 Southwest	SMF 21:20	ONT 22:56	51%	14%	0.3%	no record
WN 4984 Southwest Flight history →	SMF 21:40	ONT 23:00	58%	15%	0.3%	66%worse than usual
WN 1095 Southwest	SMF 20:18	ONT 21:15	62%	18%	0.3%	no record
WN 480 Southwest Flight history →	SMF 19:00	ONT 20:20	67%	23%	0.4%	75%worse than usual

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