Estimation Drill: Build a US Airport Count, Then Extrapolate It Worldwide

Without looking anything up, estimate how many airports the United States has, then extend your reasoning to the number of airports worldwide. ```hint Settle what counts first The total swings enormously depending on which facilities you count. Split airports into types that exist for different reasons, and pick a separate driver for each before scaling up to the world. ``` ### Clarifying Questions - Should I count only airports with scheduled passenger flights, every airfield open to the public, or every landing site including private strips, heliports and seaplane bases? - Are military air bases in scope? - Does the US figure include Alaska, Hawaii and the territories? - Would you like a single total for each, or a breakdown by type of airport? ### What a Strong Answer Covers - A clear definition of an airport, with the total split into types that grow for different reasons - A separate driver for each type, with labeled, round-number assumptions - Correct arithmetic carried through to a US figure per type and a US total - A reasoned extrapolation from the US to the world, with a justified adjustment for how aviation differs across countries - Sanity checks and a view of which assumption moves the answer most ### Follow-up Questions - Which assumption has the most influence on your total, and how would you narrow it? - If you had started from annual passenger numbers, what would you have found, and why would it differ from your answer? - How would you estimate how many new commercial airports the world will need over the next 20 years?