Definition
The last altitude or flight level assigned by ATC and acknowledged by the pilot. It remains the controlling altitude for the flight until ATC issues a new altitude assignment.
Plain English
The most recent altitude that ATC told you to fly and that you read back. Until ATC gives you a new one, that's the altitude you're expected to be at.
Context Anchor
Used in air traffic control clearances and especially in procedures for deciding what altitude to fly if radio communication is lost.
Derivation
“Assigned” comes from an older sense meaning “designated” or “set apart for a purpose.” That helps here because the altitude is not just expected or planned; it has been officially designated for your aircraft by air traffic control.
Why Pilots Care
Maintaining the last assigned altitude ensures traffic separation; deviating from it without clearance can trigger TCAS alerts or loss of separation.
Intuition Check
“Last assigned” does not mean the altitude you filed, requested, expected, or heard given to another aircraft. It means the most recent altitude given to your aircraft by air traffic control and acknowledged by you.
Example Sentence 1
After losing radio contact, the pilot maintained the last assigned altitude of 8,000 feet while continuing on the filed route.
Example Sentence 2
After a mode C discrepancy, the controller asked the pilot to confirm their last assigned altitude.