1.“What do you usually wear when you travel by plane?”
Nowadays, I'd wear hike pants (stretchier than jeans which is the other pants I use) and a t-shirt.
2. “What do you find most uncomfortable or inconvenient about your current travel clothes?”
There's always the risk that's uncomfortably cold in the plane. Or very hot. So having to carry something to put on top just in case is uncomfortable.
3. “If you could design the perfect travel outfit, what features would it have?”
cheap, a bit stretchy and light-weight.