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: DL 571 at 22:00 is the safest bet, 13% chance of being 15+ min late; the others run 20–38%.

Safest bet that day DL 571 SAN 22:00 → BOS 06:38 · 13% chance 15+ min late · usually 85% on time Riskiest WN 4930 SAN 14:35 → BOS 23:10 · 38% chance 15+ min late · usually 35% 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.


DL 571 Delta Flight history →	SAN 22:00	BOS 06:38	13%	4%	0.8%	85%
AS 390 Alaska Flight history →	SAN 07:00	BOS 15:51	20%	4%	0.8%	76%
AS 255 Alaska Flight history →	SAN 20:52	BOS 05:40	22%	5%	0.9%	85%
B6 2120 JetBlue Flight history →	SAN 20:40	BOS 05:19	24%	10%	1.4%	83%
B6 220 JetBlue Flight history →	SAN 13:06	BOS 21:51	29%	13%	1.0%	74%
B6 620 JetBlue Flight history →	SAN 10:20	BOS 19:06	29%	11%	1.0%	78%
WN 4930 Southwest Flight history →	SAN 14:35	BOS 23:10	38%	14%	0.6%	35%

Alternatives with one stop that day

All connections →


United Details →	SAN 18:55 → DEN 22:27UA 519	1h 32m Denver	DEN 23:59 → BOS 05:58 +1UA 2656	8h 03m	92%	82%
United Details →	SAN 06:20 → LAX 07:21UA 1006	1h 14m Los Angeles	LAX 08:35 → BOS 17:20UA 1783	8h 00m	94%	80%
United Details →	SAN 10:55 → DEN 14:27UA 1715	1h 36m Denver	DEN 16:03 → BOS 22:06UA 2798	8h 11m	100%	76%

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