The misconnect calculator

How long a connection should you leave?

Pick a connection at one of the 20 busiest airports: where the first flight starts, where you change, where the second flight goes, the month, and the two scheduled hours. The calculator answers with the historical chance of missing the connection at every buffer, with an interval and the flights it rests on. A connection is missed when the inbound is cancelled or diverted, or lands too late to leave 25 min to change planes.

The answers come from the live API on Fly. Its machine sleeps when idle; the page asks twice, and if it is still asleep it answers from a session recorded against the live API and says so.

Asking the API whether it is awake

Connecting atFromToTravel monthFirst flight lands atSecond flight leaves atScheduled buffer: 60 min

The chance of missing the connection, by buffer

Pick a connection

Source: the calculator's cells from the BTS on time files, live API, model .

Write token (the API's writes are token gated; this is a demonstration)

The busiest hubs, day by day

Book the first flight of the aircraft's day, and leave 65 minutes to connect at ATL

Chance of missing a connection by scheduled buffer at the three busiest hubs, with the line

Chance of missing the connection

ATL 65 min
DEN 70 min
DFW 90 min

At ATL, the busiest airport, the chance of missing a connection falls under 10% at a 65 minute buffer; the first leg of the aircraft's day is on time 85.8% of the time against 76.0% for the rest.

Source: BTS Reporting Carrier On-Time Performance, model: the misconnect curve, scheduled flights 2023 to 2026-07, as of 2026-10-01.

What the ops director would push back on

A connection on one ticket is protected: the airline holds the outbound for a late inbound with many connecting passengers and rebooks the rest. The curve counts a missed connection the way the schedule would, so it overstates misconnects for well protected connections and understates the cost of the ones missed on the last flight of the night. The calculator also works from the hub's cells shifted by each route's own average, so a route whose delays have a different shape from its hub's is answered with the hub's shape.