G.A. flying clothing ?
Lifejacket if flying over water, cap - to keep sun out of eyes ( unless flying the 747, in which case Mr. Boeing provides a perfectly useful sunshade ) shirt and trousers with lots of useful -and reachable - pockets to now hold pocket GPS, phone, small circular computer ( slide rule ) pens etc.
Entering the flight deck told the crew that this was 'our' office, remove whatever item of clothing one wished, personally I threw the tie and jacket into a corner straightaway and inserted one of those small washcloths from the passenger toilet inside my shirt collar to absorb the sweat and avoid having to button up a clammy collar at the end of the trip, looked a prat, but who cares - was my office, entry only by invitation.
QED