Plain English Meaning

These are IFR routes a pilot flies that don't follow the standard published airways and aren't covered by the FAA's published-altitude rules. Because they're not pre-checked by the FAA, the pilot or operator has to work out safe altitudes and make sure navigation and radio coverage will be available the whole way.

Full Definition

IFR routes that are not part of the published airway system and are not listed in 14 CFR Part 95 as established IFR altitudes or routes. These are typically random, point-to-point routes flown off the , often using ), and require the pilot or operator to determine , , and and navigation coverage rather than relying on values published by the FAA.