Subchapter 9.1 – Communication Failure Under IFR

IFR lost-communication procedures follow the acronym AVEFAME, which captures the hierarchy of altitudes to fly:

A – Assigned altitude (last ATC-assigned altitude)
V – Vectored altitude (the altitude you were being vectored to, if different from assigned)
E – Expected altitude (the altitude given in your clearance for a specific fix)
F – Filed altitude (the altitude in your original flight plan)
A – Assigned altitude (repeat; the safest fallback)
M – Minimum safe altitude (only as a last resort to avoid terrain)
E – Expected in airspace (non-radar environment, follow published procedures)

In practice, fly the highest of Assigned, Vectored, Expected, or Filed altitude. This ensures you maintain the maximum separation from other traffic and terrain.