How Long a Layover Needs to Be

Summary

At ATL, a layover of 74 minutes for a flight due 5–9 AM, or 133 for one due 6–9 PM, keeps the chance of a missed connection to 1 in 20. That assumes 30 minutes are needed after landing and counts only the inbound flight. Across the 20 airports with the most inbound flights, the evening figure is longer at every one, by 43 to 117 minutes. On the 481 routes into those airports with at least 1,000 flights in both windows, the median layover is 66 minutes in the morning and 144 in the evening.

Every figure in the tables below is a layover in minutes, the gap between an inbound flight’s scheduled arrival and the next flight’s scheduled departure. It has two parts. The first is the time a traveler needs after landing, to leave the aircraft, walk to the next gate and get there before the boarding cutoff. This report assumes 30 minutes, the default on the connections tool. It is an assumption, not a measurement: FlyerIntel has no gate or terminal data, and a terminal change or a large airport can take longer. The second part is the margin against a late arrival: the delay that no more than 1 in 20 of the route’s inbound flights has exceeded, read from how late its flights have actually landed. The layover is the sum of the two. Only the inbound leg is measured. The data does not know whether the next flight leaves late, whether the airline holds it, or whether the two flights are on one ticket.

Minutes, assuming 30 minutes are needed after landing. Columns are the scheduled arrival window in the arrival airport’s local time. Every airport figure pools all of the airport’s inbound routes, so it describes a flight picked at random from those arriving, not a typical route. The airports are the 20 covered airports with the most inbound flights that completed in the period, ordered here by the evening figure.

The chance that the inbound flight lands more than the layover less 30 minutes late, among flights that operated. Pooled over the 20 airports, 11,039,924 completed flights in all.

A layover shorter than the figures above is a choice to accept more risk, and the table shows how much. At 60 minutes the chance is 7.0% for a flight due 5–9 AM, 8.3% for one due 9 AM–12 PM, and 20% for one due 6–9 PM. By 120 minutes the morning figure is 2.9% and the evening figure 7.3%. The same connection is a different bet at a different hour. The gap is the accumulation of delay through the day that the site’s departure-time reports measure, seen here on arrivals.

Layover in minutes for a 1 in 20 chance of missing, assuming 30 minutes needed. The 15 routes into these airports with the most completed flights, among routes that have at least 1,000 in both windows.

The ten largest differences among the 481 routes with at least 1,000 completed flights in both windows. Those routes carry 48% of the completed inbound flights into these airports.

Cancelled and diverted flights are not in the delay record, because they end a connection differently. Among the flights scheduled into these airports, 1.62% of those due 5–9 AM were cancelled or diverted, against 2.30% of those due 6–9 PM. Flights on the same day share weather and air traffic control, so a bad afternoon raises the risk for every connection through that airport at once, and the 1 in 20 figure is an average over days, not a forecast for one. The figures say nothing about the next flight: a departure that leaves late gives a late arrival time to spare, and an airline that holds a plane or rebooks a passenger changes what a miss costs. They also assume the traveler’s own estimate of the time needed. If the walk to the next gate is longer than that, the difference comes off the margin.