Definition
An altitude restriction in an ATC clearance or on a chart meaning the aircraft must cross the specified fix at the stated altitude or any altitude higher than it, but not lower. It establishes a minimum altitude at that point while leaving the upper limit open (subject to other clearance limits or airspace constraints).
Plain English
You have to be at the named altitude or higher when you cross that point. Going lower than that altitude is not allowed.
Context Anchor
Seen on instrument procedure charts and in clearances during climbs, descents, and approaches.
Why Pilots Care
Maintains required obstacle clearance and ensures compliance with published procedures or ATC instructions.
Analogy
Think of it like a floor. You may be on the floor or above it, but you may not go below it.
Intuition Check
“At or above” does not mean the listed altitude is an exact target. It means the listed altitude is the lowest allowed altitude at that point.
Example Sentence 1
The chart shows 'Cross HOBTT at or above 6,000,' so the pilot planned the descent to be level at 6,000 by the fix rather than continuing down through it.
Example Sentence 2
The departure procedure requires climbing at or above 5,000 feet before turning.