On Wed, 03 Jan 2007 16:47:14 +0100, Mxsmanic
wrote in :

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).

Please consider doing your own research:

http://www.faa.gov/ATpubs/PCG/
RESUME OWN NAVIGATION- Used by ATC to advise a pilot to resume
his/her own navigational responsibility. It is issued after
completion of a radar vector or when radar contact is lost while
the aircraft is being radar vectored.