Brilliant question! This was a hot topic during my assessment day.
The official 'brief' is that you only need to wear a suit during your interview and your debrief (where they break the good/bad news). The first day is travelling, checking in, having a quick brief, having dinner then having a few beers/whatever your poison is and catching up with the other cadets. Don't bother wearing a suit when you're travelling (unless you don't fancy carrying it-whatever works).
The next morning is a tour/presentation from the head of flight school. My group quickly decided that we were going to be suited and booted for this part (even though it wasn't 'required'). I'd recommend you do the same. Better overdressed than under, plus it saves you getting changed before your interview. In my debrief (which by chance was with the head of flight school) he said: You were dressed smartly, you've shaved, you can tell you're not here to mess about (He didn't do my interview, he only saw me during his presentation).
Once your interview/debrief is over, we all changed into our casuals, had a few beers and celebrated.
A long answer to a quick question, but take from it what you want
