On Sat, 4 Sep 2004, Barry wrote:

In this same regard, the FAA has determined that a certificated flight
instructor on board an aircraft for the purpose of providing flight
instruction, who does not act as pilot in command or function as a
required flight crewmember, is not performing or exercising pilot
privileges that would require him or her to possess a valid medical
certificate under the FARs."

So can a CFI without a valid medical give flight training to a student
pilot who has a current medical, but not a private certificate? In this
case, is the student or the CFI acting as PIC? It looks like that's what
the answer hinges on. Does it make a difference whether the student is
pre- or post-solo?

-Dan