Today looks rough: weather pushes the average chance of arriving 15+ min late to 40%, against 28% on a calm day. Safest: DL 1780 at 08:51, 33%.

Safest bet today DL 1780 BOS 08:51 → SJU 12:58 · 33% chance 15+ min late · usually 78% on time Riskiest B6 561 BOS 18:49 → SJU 22:53 · 48% chance 15+ min late · usually 51% on time

Weather 40% average chance a nonstop arrives 15+ min late; 28% 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. 1 flight that already left today is not shown.


DL 1780 Delta Flight history →	BOS 08:51	SJU 12:58	33%	4%	0.5%	78%worse than usual
B6 861 JetBlue Flight history →	BOS 08:00	SJU 12:04	38%	8%	0.5%	75%worse than usual
B6 561 JetBlue Flight history →	BOS 18:49	SJU 22:53	48%	21%	0.7%	51%

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