FAA Airline Transport Pilot (ATM)Navigation, Air Traffic Control and ProceduresMedium
A dispatcher is planning a domestic cruise altitude of FL450. In which class of airspace will the flight operate, and what are its published vertical limits?
- AClass E airspace, from 14,500 feet MSL up to FL600
- BClass B airspace, from the surface up to 10,000 feet MSL
- CClass A airspace, from FL180 up to FL450 only
- DClass A airspace, from 18,000 feet MSL up to and including FL600
Show answer & explanationAnswer & explanation
Correct answer: D. Class A airspace, from 18,000 feet MSL up to and including FL600
Class A airspace extends from 18,000 feet MSL up to and including FL600 over the continental United States. FL450 falls within this range, and IFR operation with an ATC clearance is required throughout Class A airspace.
Why the other options are wrong
- A. Class E has variable lower limits but does not extend to FL600 as the primary class above 18,000.
- B. Class B is terminal airspace around major airports, not enroute high-altitude airspace.
- C. Class A extends beyond FL450, all the way to FL600, so this range is too limited.
Class A Airspace
Class A airspace extends from 18,000 feet MSL up to and including FL600 within the continental U.S., requiring IFR flight plans and ATC clearance for all operations.
- Lower limit: 18,000 feet MSL
- Upper limit: FL600
- IFR only, no VFR operations permitted
- Requires an ATC clearance and IFR flight plan
Memory trick: 'A for Altitude — 18 grand to 60 grand, IFR demand'