What a Late Aircraft Costs the Next Flight

Summary

When the aircraft that flew a flight in had landed 30 or more minutes late, the next flight left 15 or more minutes late 99% of the time on a turn scheduled under an hour, and 42% with 90 minutes to 6 hours. Measured on 19,440,732 departures whose aircraft’s previous flight is known, not inferred from the DOT’s cause codes.

The DOT file names the aircraft that flew each flight. Sorting one aircraft’s flights by scheduled departure gives its day: where it went, and when. For every departure the report finds the flight the same aircraft flew into that airport just before, and takes two things from it: how late it landed, and how long the schedule gave the aircraft on the ground before this flight was due to leave. 19,440,732 departures have such a flight, 90.9% of the 21,380,414 that left the gate. Of those, 20.1% left 15 or more minutes late, and 20.7% followed an aircraft that had landed 15 or more minutes late. Nothing is inferred from the DOT’s cause codes. They are compared with the measurement further down.

Share of departures that left 15 or more minutes late, by how late the aircraft’s previous flight landed (columns) and how long the schedule gave it on the ground (rows). A dash is a cell under 120 departures.

When the aircraft had landed 30 or more minutes late, the next flight left 15 or more minutes late 99.0% of the time if the schedule gave it under an hour on the ground (931,340 departures). With 90 minutes to 6 hours it was 41.6% (427,658 departures). The rate first falls below half in the band of 3 to 6 hours, where it is 27.9%. After a night on the ground, 6 hours or more, it was 13.6%. When the aircraft landed on time or early, flights left 15 or more minutes late between 9.1% and 12.0% of the time on the same turns. A short turn leaves the aircraft no time to give back.

Departures whose aircraft’s previous flight landed 30 or more minutes late, against departures whose aircraft landed early or on time. A dash is a row under 120 departures.

After an aircraft that landed 30 or more minutes late, with under an hour scheduled, the next flight left an average of 85 minutes late behind an aircraft that had landed an average of 76 minutes late, so the flight left later than the aircraft had landed. With 90 minutes to 6 hours on the ground the same figures are 32 minutes at pushback against 98 on landing, so most of the delay was gone before the next flight left. These averages include the departures that left on time.

Same-day turns only, under 6 hours. The expected figure applies the other full-period airlines’ rate in each turn band to this airline’s own mix of turns, so the gap is what is left after the length of its turns is taken out. Airlines that did not report every month are shown with their months and are not compared.

The share of same-day rotations scheduled with under 45 minutes on the ground runs from 0.5% at Allegiant Air to 48.3% at Envoy Air among the 12 airlines that reported every month. After an aircraft that landed 30 or more minutes late, Delta Air Lines, Frontier Airlines and JetBlue left 15 or more minutes late more often than the turns they schedule would give (+5.0 points at Delta Air Lines). SkyWest Airlines, Envoy Air and Republic Airways left late less often than their turns would give (-6.5 points at SkyWest Airlines). The gap compares each airline with the others at the same ground time. It says how the delay was passed on and does not say why: an airline’s spare aircraft, the airports it flies from and the hour of the day all sit inside it. Spirit Airlines, Endeavor Air and Hawaiian Airlines did not report every month and are shown but not compared.

Across the 64 covered airports with at least 500 late departures, 57.0% of the departures that left 15 or more minutes late followed an aircraft that had landed 15 or more minutes late. By airport it runs from 47.1% at BWI to 73.1% at MYR, with a median of 61.6%. A low share means more of an airport’s lateness started there, with an aircraft that had arrived on time. The airlines and hours at an airport are not the same as at any other, so the share describes departures from that airport and does not rate it.

Covered airports with at least 500 late departures with a known inbound aircraft. The rest of each airport’s late departures followed an aircraft that came in on time or early.

Airlines report a cause for the delay on a flight that arrives 15 or more minutes late, and one cause is a late-arriving aircraft. Among the 3,899,379 such flights with a known inbound aircraft, 2,037,056 carry late-aircraft minutes, and 80.9% of them followed an aircraft that had landed 15 or more minutes late. Of the 1,862,323 without those minutes, 22.0% did. Turned round, 80.1% of the flights whose aircraft landed 15 or more minutes late carry late-aircraft minutes, and so do 21.2% of those whose aircraft landed on time or early. The code follows the measurement closely and is not the same thing.

A flight the airline cancelled never left, so it is not in any figure, and this report cannot say how often a late aircraft ends in a cancellation. The DOT records the tail number of the aircraft that flew each flight, so a flight the airline covered with a substitute is matched to the aircraft that flew it and not to the late one it was first planned for; the figures describe the flight each aircraft went on to fly. They do not follow a passenger. A link is dropped when the aircraft’s previous flight is unknown, diverted or has no arrival time, when two of its flights share a scheduled minute, when the schedule puts the next flight out before the inbound is due in, when the aircraft sat for more than 12 hours, and when the reported times put the inbound at the gate after the next flight had left. Scheduled times are local to each airport, and the arrival date of a flight is worked out from its two clock times.