Today: UA 1866 at 22:25 is the safest bet, 15% chance of being 15+ min late; the others run 16–56%.

Safest bet today UA 1866 IAD 22:25 → BOS 00:24 · 15% chance 15+ min late Riskiest UA 1392 IAD 12:55 → BOS 14:40 · 56% chance 15+ min late · usually 82% on time

Against a calm day 26% average chance a nonstop arrives 15+ min late; 16% 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.


UA 1866 United	IAD 22:25	BOS 00:24	15%	9%	0.7%	no record
UA 755 United Flight history →	IAD 22:10	BOS 23:59	16%	7%	0.7%	81%
UA 3615 United flown by Republic Flight history →	IAD 15:30	BOS 17:24	16%	8%	0.8%	65%
YX 3503 Republic	IAD 15:18	BOS 17:22	17%	7%	0.7%	no record
UA 688 United Flight history →	IAD 17:25	BOS 19:14	30%	14%	0.7%	63%
UA 641 United Flight history →	IAD 08:35	BOS 10:20	31%	10%	1.1%	92%worse than usual
UA 1392 United Flight history →	IAD 12:55	BOS 14:40	56%	25%	1.0%	82%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