"§97.5 Station license grant required.
(a) The station apparatus MUST BE UNDER THE PHYSICAL CONTROL of a person
named in an amateur station license grant on the ULS consolidated
license database or a person authorized for alien reciprocal operation
by §97.107 of this part, before the station may transmit on any amateur
service frequency from any place that is:"

Response: N1547C set up a track just as I mentioned and the control
operator was not on the aircraft. The FCC knew about it (many years ago)
and thee were no problems. You do not need to be physically present at a
transmitter site to have physical control over the amateur station. For
example, I can place my station remotely and use a link to operate it. In
that case, I have physical control over it and am in compliance with part
97. Similarly, I can have a telephone nearby and a person present and make
a telephone call to tell the person to turn the transmitter off. I am the
control operator and the transmitter is under the physical control of me.

If I turn the APRS transmitter on before flight, then turn it off after the
flight, there is no question that I am in control, as long as I have a radio
link with the non-ham pilot to be able to tell him to turn off the APRS
transmitter, or I can turn it off after the flight. It need not be
immediate. This assumes the non ham is not able to change frequency or use
a mike or other things - which would not happen in an APRS installation. A
sanitary installation would have everything in a sealed box, with just an
on-off switch.

A "gray" area would occur if the non-ham operator could arbitrarily turn the
APRS unit on, but there are "work arounds". If the transmitter is connected
to the ignition switch of the aircraft, so that being turned on is
incidental to the operation of the aircraft, then it could be argued that
the non-ham does not have control. And, it would ber better if the on-off
switch was not resetable, which means it could be turned off, but not turned
on.

It also could go into a sleep mode, unless the aircraft was moving and never
be turned on by the non-ham. When the pilot returned to where th eham was,
it could be shut off.

Hams have been operating in "gray" areas for years and it is not a big
issue. I operate a ham repeater and have for decades. For some period of
time, they operated in a gray area. Similarly, hams have been connecting to
the internet for years, even though that is also a gray area.

Colin Lamb