Today: DL 1526 at 05:30 is the safest bet, 7% chance of being 15+ min late; evening flights run 15–25%.

Safest bet today DL 1526 SMF 05:30 → SLC 08:12 · 7% chance 15+ min late · usually 97% on time Riskiest WN 3828 SMF 18:35 → SLC 21:20 · 25% chance 15+ min late · usually 62% on time

Against a calm day 15% average chance a nonstop arrives 15+ min late; 13% 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.


DL 1526 Delta Flight history →	SMF 05:30	SLC 08:12	7%	3%	0.4%	97%
WN 4021 Southwest	SMF 07:25	SLC 10:10	10%	2%	0.1%	no record
WN 3827 Southwest Flight history →	SMF 08:05	SLC 10:40	12%	2%	0.1%	95%
DL 1797 Delta	SMF 13:26	SLC 16:10	14%	4%	0.7%	no record
DL 1342 Delta Flight history →	SMF 17:00	SLC 19:41	15%	5%	0.7%	83%
DL 2585 Delta Flight history →	SMF 19:20	SLC 22:02	15%	5%	0.7%	91%
DL 1423 Delta Flight history →	SMF 13:36	SLC 16:13	16%	5%	0.7%	88%
DL 1367 Delta Flight history →	SMF 09:45	SLC 12:27	16%	3%	0.3%	92%
WN 3976 Southwest	SMF 20:50	SLC 23:35	22%	6%	0.5%	no record
WN 3828 Southwest Flight history →	SMF 18:35	SLC 21:20	25%	6%	0.5%	62%

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