Estimation question

How many commercial flights fly in a day?

Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.

What this question tests

Tests structured Fermi estimation combining airport counts, flight frequency and reasonable global assumptions.

Frame the formula: number of major airports globally times an average number of daily departing flights per airport.
Assume roughly 5,000 airports worldwide handle regular scheduled commercial traffic, though only a fraction are truly major hubs.
Assume major hub airports average around 500 to 1,000 daily flights each, roughly 500 such hubs, while thousands of smaller airports average only a handful of flights per day.
Calculate hub contribution: 500 hubs times roughly 700 flights each gives roughly 350,000 flights, and add a smaller contribution from thousands of minor airports, roughly another 50,000 to 70,000.
State a combined estimate of roughly 100,000 to 120,000 commercial flights globally per day, adjusted down from the hub-only figure to avoid double-counting since each flight has two endpoint airports.

Separates major hubs from smaller airports, recognizing flight volume isn't evenly distributed across all airports.
Explicitly corrects for double-counting, since each flight touches two airports, a detail many estimates miss.
Shows the full calculation clearly, making each assumption easy to challenge or adjust independently.

Treating all airports as having similar flight volume, ignoring the concentration of traffic at major hubs.
Forgetting to correct for double-counting flights that are counted at both their departure and arrival airport.

How would you sanity-check this against a number you might recall, like total annual global flights?
How would this estimate change if you separated domestic from international flights?