I wear pants that are tapered at the ankle (so they don’t touch the bathroom floor).

I also wear a long-sleeved t-shirt and perhaps a cardigan or zip-up hoodie so I won’t get cold.

I like Varley. I’ll also sleeve Vuori joggers with a fleece.

dress and flats

I like wide leg sweatpants but I think people who say that joggers are much better in an airplane bathroom have a good point.

For my overnight flight, I’m wearing a hoodie and my comfy Lou and Grey sweatpants plus sneakers.

I wear jeans on long flights, I have a couple of pairs that are very stretchy and soft that I use for these situations. And then I layer up on top. Maybe a camisole, shirt, then cardigan/open sweater on top. Sometimes these planes can be cold! Shoe wise I wear the bulkiest shoes I'm bringing. I always have an eye shade, I find it's easier for me to try to snooze when I'm wearing the shade than when not. Finally I wear glasses on the plane (my eyes get way too dry in contacts when flying). I use a chain to put my glasses around my neck when I snooze...maybe I'm overly cautious but I want to have my glasses immediately available if there's an emergency. One more thing, I usually wear black on top because it won't show much if I get overly sweaty (thank you menopause) or spill something on myself, lol.

Compression socks

I like Prana's Send Off pants for travel
https://www.prana.com/p/send-off-pant/2066001.html

Add a t-shirt and a cardigan.