Plain English Meaning

These are the altitudes a pilot is allowed or required to fly while cruising under instrument rules, between leaving the departure airport area and arriving at the destination area. Each altitude type is set to keep the aircraft safely above terrain, within range of navigation signals, and clear of other traffic.

Full Definition

The set of published or assigned altitudes used by aircraft operating under Instrument Flight Rules during the en route phase of flight, between the departure and arrival terminal areas. These altitudes are designed to provide adequate , signal reception, and from other traffic. They include categories such as (), (), Minimum Reception Altitude (MRA), (MAA), and (OROCA), each serving a or navigation purpose along an or .