Do Bigger Airports Run Later

Summary

22.5% of departures at the largest third of covered airports left 15 or more minutes late, against 18.7% at the smallest. Across 64 airports, the delay rate rises with airport size, with a rank correlation of 0.57. Cancellations ran at 1.54% in the largest third and 1.48% in the smallest.

64 covered airports with at least 5,000 scheduled departures, ordered by scheduled departures and cut into thirds of 21, 21 and 22 airports. The largest third ran a higher departure delay rate than the smallest, 22.5% against 18.7%, a gap of 3.8 points. Cancellations ran at 1.54% in the largest third and 1.48% in the smallest, and 21.3% of arrivals at the largest were 15 or more minutes late against 22.3% at the smallest.

Counts added up across the airports of the group and divided once, so a large airport weighs more than a small one inside its group. Departure delay is the share of departed flights that left 15 or more minutes after schedule; arrival delay is the share of completed arrivals; cancelled is cancelled over scheduled departures.

Spearman rank correlation across the 64 airports, each airport counted once whatever its size. A value of one would put the busiest airport at the top of the rate every time, zero means no pattern, and the Reading column calls a value under 0.2 weak and one from 0.5 clear. It describes how the ranks line up and says nothing about cause.

The 10 covered airports with the most scheduled departures in the data.

The airport of each group with the lowest share of departures delayed 15 or more minutes and the airport with the highest, each airport on its own counts.

Middle third has the widest spread between its airports, 14.1 points from HNL to FLL. The groups overlap: the lowest rate in one group sits below the highest rate of the group next to it, so knowing an airport's size does not place it. A size group is not a forecast for one airport on one day. The report on the most reliable major airports ranks them one at a time, and the delay rate of any airport is on its own page.

Size here is scheduled departures in the data, at covered airports only. It does not separate the airports that serve a hub airline from those that do not, or the airports in the north from those in the south, and both are mixed into every group. Rank correlation ignores how far apart two airports are in size. Share of scheduled departures: largest third 64.9%, middle third 25.1% and smallest third 10.1%.