Guides
Flight reliability, explained
Practical, plain-English guides to how flight delays work and what the data says — built on the same public U.S. DOT (BTS) records as the rest of OnTimeStats, 2000–2025.
How the numbers work
Understand the figures
What does “on-time” actually mean?
The U.S. DOT 15-minute standard explained: what counts as on-time, why it's measured at the gate, and how cancellations and diversions are handled.
Understanding flight delays
The five official causes of flight delays the government tracks — carrier, late-arriving aircraft, the air-traffic system, weather, and security — and what each one means for you.
Our full methodology
Exactly how every number on the site is measured, sourced, and bounded — the complete reference.
Practical travel advice
Plan your trip
When to arrive at the airport
How early to get to the airport for domestic and international flights, what TSA PreCheck changes, and the cutoff times that actually make you miss a flight.
How much layover time do you really need?
Minimum connection times, why they differ by airport and for international arrivals, what makes a connection risky, and your rights if an airline delay makes you miss it.
Rankings from our data
See what the data says
The worst U.S. airports for delays
Major U.S. airports ranked by on-time arrival rate, from the most reliable to the most delay-prone, using public DOT flight records.
The most on-time U.S. airlines
U.S. airlines ranked by their on-time arrival rate over the full window we cover, with the number of flights behind every figure.
The most reliable U.S. flight routes
The busy U.S. routes with the best on-time records — and the worst — ranked from public DOT data with full flight counts.
The best and worst months to fly
How U.S. flight delays rise and fall across the calendar year, so you can see which months historically fly the smoothest.