Connection risk calculator

For the inbound route, the calculator takes every flight that actually arrived and sorts the arrival delays into 5-minute slices from 30 minutes early to 4 hours late. The slack is the layover minus the time you need to change planes; the share of arrivals later than that slack is the chance of landing too late. Cancelled and diverted flights never arrive, so they count as a missed connection in full, weighted by how often they happened on that route. The onward flight is assumed to leave on time, which is the cautious reading. Only routes with at least 365 flights over the period are offered, the same floor the rest of the site uses.

Definitions and limits are on the methodology page. Airline minimum connection times vary by airport and terminal, so check your airline’s figure before trusting a short layover. To find the most reliable direct option for a trip in the first place, use the trip planner. For a hub-by-hub table of how often 45, 60 and 90 minute connections fail, see missed connection risk at the major US hubs.