Same City, Different Airport

Summary

8 cities have two or more covered airports. In 6 of them the airports are within 3 points in the share of departures that leave 15 or more minutes late; Washington is the widest at 11.1 points. For the same airline at two airports of one city, the airport that is later overall was also later for the airline in 24 of 47 pairs.

8 cities have two or more covered airports, 21 airports in all. In 6 of the cities the airports are within 3 points of each other in the share of departures that leave 15 or more minutes late. Dallas–Fort Worth is the closest, DAL at 27.4% and DFW at 27.5%, a gap of 0.1 points. Washington is the furthest apart, IAD at 17.0% and BWI at 28.1%, 11.1 points. The second half of the report asks whether an airport’s place in its city belongs to the airport or to the airlines that fly from it, by following one airline from one airport of a city to another.

Covered airports with at least 5,000 departures, grouped by the city area the airport belongs to, the widest gap first and the airport that leaves late least often first within each city. Left late is the share of departures leaving 15 or more minutes after the scheduled time. Landed on time is the share of flights arriving there that arrived under 15 minutes late. Cancelled is the share of scheduled departures.

Same figures as the table above, one row per city; the least late airport is the one where the smallest share of departures leaves late. Gap is the share of departures leaving 15 or more minutes late at the airport where it is highest minus the share at the airport where it is lowest.

For every airline with 10,000 or more departures at each of two airports in one city there are 47 pairs. In 24 of them (51%) the airline left late more often at the airport that is later for all airlines together, which is what the airport alone would predict; in the rest it was the other way round. The typical pair differs by 3.3 points for the same airline, in either direction, where the same two airports differ by 0.9 points for all airlines together. The order of two airports for all airlines together is not a reliable guide to the order for one airline. The widest city, Washington, shows how the airline mix enters. At BWI, Southwest Airlines flew 75% of the departures and left late 30.7% of the time, while every other airline together left late 20.3% of the time, which is 3.3 points above the IAD figure for all airlines, against 11.1 points with Southwest Airlines included.

Airline and airport pairs with at least 10,000 departures at each airport, the 10 with the widest difference in either direction. The first airport is the one in the pair that is on time more often for all airlines together. Difference is the airline’s share left late at the second airport minus at the first, so a positive figure means the airline is later where the airport is later overall.

The share leaving late describes the airport and the airline together; the same airline at a small airport flies different routes, at different hours, with a different aircraft rotation than at its large one, and none of that is held fixed. Airports of a city differ in the destinations they serve and in the weather they get, though they sit close together. A city is as the site groups airports into city areas, and only covered airports count, so an airport the site does not cover is not in its city here. The rates are over the whole period and say nothing about a particular day. A pair with the floor of 10,000 departures has a standard error under half a point, which is smaller than most of the differences listed but not all of the pairs.