Today: WN 818 at 07:45 is the safest bet, 7% chance of being 15+ min late; evening flights run 23–30%.

Safest bet today WN 818 DEN 07:45 → BOI 09:45 · 7% chance 15+ min late · usually 90% on time Riskiest UA 2014 DEN 19:28 → BOI 21:29 · 30% chance 15+ min late · usually 73% on time

Against a calm day 18% average chance a nonstop arrives 15+ min late; 17% 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 818 Southwest Flight history →	DEN 07:45	BOI 09:45	7%	1%	0.1%	90%
UA 255 United	DEN 07:43	BOI 09:46	9%	3%	0.1%	no record
WN 2107 Southwest	DEN 08:50	BOI 10:50	9%	1%	0.1%	no record
UA 2255 United Flight history →	DEN 11:36	BOI 13:35	14%	3%	0.4%	82%
WN 1491 Southwest Flight history →	DEN 12:50	BOI 14:45	16%	2%	0.4%	62%
WN 1551 Southwest	DEN 13:15	BOI 15:15	18%	3%	0.4%	no record
UA 2602 United Flight history →	DEN 15:55	BOI 17:56	23%	5%	0.5%	67%
UA 5923 United flown by SkyWest Flight history →	DEN 20:25	BOI 22:37	23%	6%	0.6%	71%
WN 3806 Southwest Flight history →	DEN 20:55	BOI 23:00	25%	6%	0.5%	40%
WN 4421 Southwest	DEN 20:55	BOI 22:54	30%	5%	0.5%	no record
UA 2014 United Flight history →	DEN 19:28	BOI 21:29	30%	6%	0.5%	73%

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