Today: DL 635 at 23:10 is the safest bet, 15% chance of being 15+ min late; the others run 15–33%.

Safest bet today DL 635 BOI 23:10 → ATL 05:16 · 15% chance 15+ min late · usually 78% on time Riskiest DL 874 BOI 14:03 → ATL 20:19 · 33% chance 15+ min late · usually 89% on time

Against a calm day 21% 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.


DL 635 Delta Flight history →	BOI 23:10	ATL 05:16	15%	5%	0.8%	78%
DL 704 Delta Flight history →	BOI 23:12	ATL 05:37	15%	5%	0.8%	77%
DL 874 Delta Flight history →	BOI 14:03	ATL 20:19	33%	5%	0.3%	89%worse than usual

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