Definition
The published lower and upper altitude limits that define the vertical boundaries of a block of airspace, such as a Special Use Airspace area, MOA, restricted area, or warning area. The floor is the lowest altitude at which the airspace becomes active; the ceiling is the highest altitude to which it extends. Aircraft operating below the floor or above the ceiling are outside that airspace and its associated restrictions.
Plain English
The bottom and top altitudes of a chunk of airspace. Below the floor or above the ceiling, you are not in that airspace.
Context Anchor
Seen when reviewing special use airspace on charts, procedures, or preflight planning information.
Derivation
Floor and ceiling are borrowed from the way we describe a room: the surface below you and the surface above you. Aviation uses the same image vertically through the sky to mark the bottom and top of an airspace block.
Why Pilots Care
Knowing the exact floors and ceilings prevents inadvertent entry into active special use airspace and allows safe route planning or altitude selection.
Intuition Check
Do not picture a physical floor or ceiling in the sky. These are published altitude limits that define the bottom and top of an airspace area.
Example Sentence 1
The MOA had a floor of 8,000 feet MSL and a ceiling of 17,000 feet MSL, so the pilot filed at 7,000 feet to remain below it.
Example Sentence 2
Before filing a direct route, verify the floors and ceilings of the restricted area on the chart.