Definition
An altitude shown on Jeppesen en route charts within a latitude/longitude grid block (typically one degree by one degree) that provides obstacle clearance over the entire block. The Grid MORA gives 1,000 feet of clearance above the highest terrain or obstacle in that block where the highest elevation is 5,000 feet MSL or lower, and 2,000 feet of clearance where the highest elevation is above 5,000 feet MSL. Grid MORAs are not flight-checked for navigation signal reception and are advisory altitudes, not ATC-assigned minimums.
Plain English
A safe altitude printed inside each grid square on a chart. If you fly at or above that number anywhere in the square, you are guaranteed to clear all the terrain and obstacles inside it.
Context Anchor
Seen on instrument enroute charts when planning or checking flight away from published routes, especially across high or uneven terrain.
Derivation
‘Grid’ refers to the latitude/longitude squares on the chart. ‘Minimum Off Route’ means this is the lowest safe altitude when you are not on a published airway or route — in other words, off-route. The name tells you exactly when it applies: when you are flying through that grid square but not following a charted route that already has its own minimum altitude.
Why Pilots Care
They let you safely fly direct or deviate from airways without hitting terrain or obstacles.
Grounding Statement
Picture one square on the chart: the grid MORA is high enough to clear the tallest thing in that square by the required margin.
Intuition Check
A grid MORA is not the minimum safe altitude for every purpose. It is an obstacle-clearance number for a chart grid, not a promise of communications, navigation reception, or an air traffic control clearance.
Example Sentence 1
After deviating around a line of thunderstorms, the pilot climbed to the Grid MORA shown in that chart block to ensure terrain clearance until back on course.
Example Sentence 2
In the mountainous grid the MORA was set 2,000 feet above the highest peak to maintain the required margin.