Today looks like a normal day here: all 3 nonstops are 6–11% likely to arrive 15+ min late.

Safest bet today UA 3438 SDF 06:00 → IAD 07:35 · 6% chance 15+ min late · usually 93% on time Riskiest UA 3717 SDF 10:05 → IAD 11:45 · 11% chance 15+ min late · usually 86% on time

Against a calm day 8% average chance a nonstop arrives 15+ min late; 5% 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. Dimmed: airlines we don’t forecast yet, shown with their 12-month record if they usually fly that weekday.


UA 3438 United flown by Republic Flight history →	SDF 06:00	IAD 07:35	6%	3%	0.5%	93%
UA 3508 United flown by Republic Flight history →	SDF 10:07	IAD 12:07	7%	3%	0.5%	88%
UA 3717 United flown by Republic Flight history →	SDF 10:05	IAD 11:45	11%	4%	0.5%	86%
UA 4067 United flown by Mesa no forecast: 12-month record	SDF 13:48	IAD 15:32	14%	6%	1.2%	86%

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