Today looks rough: weather pushes the average chance of arriving 15+ min late to 49%, against 20% on a calm day. Safest: AA 4727 at 18:00, 42%.

Safest bet today AA 4727 STL 18:00 → BOS 21:55 · 42% chance 15+ min late · usually 81% on time Riskiest WN 2443 STL 20:00 → BOS 23:35 · 63% chance 15+ min late

Weather 49% average chance a nonstop arrives 15+ min late; 20% 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. 6 flights that already left today are not shown.


AA 4727 American flown by Republic Flight history →	STL 18:00	BOS 21:55	42%	22%	0.4%	81%worse than usual
AA 4678 American flown by Republic Flight history →	STL 19:50	BOS 23:37	42%	18%	0.5%	59%
WN 3497 Southwest	STL 21:06	BOS 00:51	49%	19%	0.2%	no record
WN 2443 Southwest	STL 20:00	BOS 23:35	63%	21%	0.2%	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 Sun, Oct 4 (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