Definition
Published altitude requirements on a departure, arrival, or instrument procedure that specify a minimum altitude, maximum altitude, mandatory altitude, or a window between two altitudes that an aircraft must meet at a specific fix or waypoint. Restrictions are depicted on charts with lines above, below, or both above and below the altitude figure, indicating at-or-above, at-or-below, or mandatory crossing requirements.
Plain English
Rules printed on a procedure chart telling you how high or low you must be when you cross a certain point. They might say 'be at or above this height,' 'be at or below this height,' 'be exactly at this height,' or 'be somewhere between these two heights.'
Context Anchor
Seen on instrument departure procedures, arrival procedures, approach charts, and in air traffic control instructions.
Derivation
Altitude comes from the Latin word altus, meaning high. Restriction comes from a Latin idea meaning to bind or hold back. Together, the phrase points to a height that is not freely chosen; it is limited by the procedure or instruction.
Why Pilots Care
They ensure terrain clearance, traffic separation, noise abatement compliance, and legal adherence to the published procedure.
Intuition Check
Do not read altitude restrictions as helpful suggestions. In this context, they are required altitude limits unless air traffic control changes them.
Example Sentence 1
The SID showed an altitude restriction of 'at or above 5,000' at WAVES, so the crew planned the climb to be through that altitude before crossing the fix.
Example Sentence 2
We reviewed the altitude restrictions on the arrival chart to confirm the aircraft could meet the climb gradient.