Today: WN 4981 at 05:45 is the safest bet, 2% chance of being 15+ min late; evening flights run 10–22%.

Safest bet today WN 4981 SLC 05:45 → SMF 06:25 · 2% chance 15+ min late · usually 95% on time Riskiest WN 3893 SLC 20:30 → SMF 21:19 · 22% chance 15+ min late

Against a calm day 12% average chance a nonstop arrives 15+ min late; 11% 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.


WN 4981 Southwest Flight history →	SLC 05:45	SMF 06:25	2%	1%	0.1%	95%
WN 3892 Southwest	SLC 07:00	SMF 07:49	3%	1%	0.1%	no record
DL 1367 Delta Flight history →	SLC 08:10	SMF 08:51	5%	2%	0.2%	93%
DL 1582 Delta Flight history →	SLC 23:04	SMF 23:44	10%	3%	0.7%	90%
DL 1342 Delta Flight history →	SLC 15:25	SMF 16:07	14%	5%	0.6%	83%
DL 2585 Delta Flight history →	SLC 17:35	SMF 18:16	14%	5%	0.6%	84%
DL 1423 Delta Flight history →	SLC 11:35	SMF 12:16	16%	4%	0.2%	86%
WN 3757 Southwest Flight history →	SLC 20:15	SMF 20:55	22%	5%	0.4%	54%
WN 3893 Southwest	SLC 20:30	SMF 21:19	22%	5%	0.4%	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 Mon, Oct 5 (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