Definition
A published segment of an airway where the Minimum Enroute Altitude (MEA) does not provide guaranteed navigation signal coverage from the ground-based navigation aids defining that route. The gap is charted, its length is specified, and pilots may legally fly through it provided they can maintain course by other approved means.
Plain English
A short stretch of an airway where the normal minimum altitude is high enough for terrain and obstacles, but the navigation signal from the ground stations may fade out. The chart tells you where the gap is and how long it is.
Context Anchor
Seen on IFR en route charts near a charted minimum en route altitude for an airway or route segment.
Derivation
MEA stands for Minimum Enroute Altitude. 'Gap' is used in its everyday sense -- a break or interruption. Together: a break in the signal coverage that would normally be available at the MEA.
Why Pilots Care
Pilots must recognize an MEA GAP to select an appropriate altitude that maintains required clearance rather than assuming the prior MEA still applies.
Intuition Check
Do not read MEA GAP as a missing altitude or a gap in obstacle clearance. The gap is a short break in guaranteed navigation signal coverage at the published MEA.
Example Sentence 1
Reviewing the chart before departure, she noted an MEA gap of 12 nautical miles between the two VORs and planned to use GPS to maintain the course through it.
Example Sentence 2
During route planning the presence of an MEA GAP prompted the pilot to verify terrain elevation and select a safe altitude from the chart.