Larry Dighera writes:

Above 18,000' is Class A airspace. It's also called positive control
airspace; you won't get a "resume own navigation" instruction in Class
A airspace.

You can request lower from ATC, but until you are given a new
altitude, you must maintain that for which you are cleared.

OK. Does that apply to lateral navigation as well? Nobody seems to
object when I let the FMC follow the lateral course as filed (at least
during the en route phase of the flight).

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