Never forgotten how out of place I found myself when I was upgraded from Economy to Business in DXB, flying DXB-AMS having come off overnight MEL-DXB in Economy.
In the planning for this long haul flight to AMS, I had specifically worn my oldest, rattiest tracksuit pants as I'd planned on ditching them in AMS, a hoodie, a beat up superman t-shirt with holes in it, and thongs. Having just balled my eyes out to wreck it ralph having been an emotional wreck after taking one too many sleeping pills washed down with whisky... I've never felt more out of place in my life.
Now in the points world (so F/J) - usually a pair of dress shorts and a shirt, transfer into SQ PJs once onboard to sleep/rest, then once I've decided I'm done sleeping and/or close enough to arrival - change back into normal clothes.