Definition
Airports designated on a flight plan or in flight planning as suitable destinations if the intended destination becomes unreachable or unsafe to land at due to weather, equipment problems, airport closures, or other operational factors.
Plain English
A backup airport you have already picked out and planned for, so that if you cannot land at your planned destination, you have somewhere else to go that you know will work.
Context Anchor
You see this term during flight planning, route review, weather decision-making, and risk discussions before or during a flight.
Derivation
From the Latin alternare, meaning 'to do by turns' or 'one after the other.' An alternate airport is the 'other turn' you take when the first choice does not work out.
Why Pilots Care
Regulations require carrying enough fuel to reach an alternate, ensuring a safe landing option remains available.
Intuition Check
“Alternate” does not just mean any different airport nearby. In this context, it means a practical backup airport that the pilot could actually use if the planned airport is no longer suitable.
Example Sentence 1
Because of forecast thunderstorms at the destination, the instructor had the student select two alternate airports and verify that fuel reserves would cover reaching either one.
Example Sentence 2
During preflight, the instructor reminded the student to verify fuel reserves to the alternate airports.