Friday, October 9 · typical odds for a Friday (too early for a weather forecast) · issued Sun 4:00 PM ET · 7 nonstops

Fri, Oct 9: WN 4911 at 06:00 is the safest bet, 2% chance of being 15+ min late; evening flights run 30–33%.

Safest bet that day WN 4911 SMF 06:00 → ONT 07:20 · 2% chance 15+ min late · usually 97% on time Riskiest WN 480 SMF 17:30 → ONT 18:55 · 33% chance 15+ min late · usually 75% 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 4911 Southwest Flight history →	SMF 06:00	ONT 07:20	2%	1%	0.6%	97%
WN 3805 Southwest Flight history →	SMF 09:10	ONT 10:30	6%	2%	0.6%	92%
WN 300 Southwest Flight history →	SMF 12:00	ONT 13:25	18%	4%	0.6%	71%
WN 3807 Southwest Flight history →	SMF 14:00	ONT 15:20	23%	5%	0.6%	83%
WN 3808 Southwest Flight history →	SMF 16:15	ONT 17:35	30%	8%	0.6%	38%
WN 4984 Southwest Flight history →	SMF 20:55	ONT 22:20	32%	11%	0.6%	66%
WN 480 Southwest Flight history →	SMF 17:30	ONT 18:55	33%	9%	0.6%	75%

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