In 2017 I took a ten day ski trip by plane with only an under-the-seat "personal bag".
I usually overpack a little bit, but in 2017 I had a ten day ski trip by airplane where several factors converged for really light packing. I was flying alone on Frontier (first time on that airline) and determined to avoid baggage fees. they only allow one free personal bag (purse, laptop, briefcase), meant to fit under your seat. all other bags cost a fee. so the only thing I took was a medium backpack. I could barely get it zipped when i put my ski boots in it, but i was also able to pack in a couple underlayers, socks, a few select toiletries/meds, and other small articles. My ski goggles made it in there too somewhere. I wore on my body my ski jacket, ski vest, and ski pants, sturdy hiking boots, and carried my helmet in my hand and later was able to stow helmet and jacket in the overhead bin. The backpack was kind of bulging for going under the seat, but they let me stow it down there by my feet anyway.
Fortunately, I was able to cheat a little on this trip because I was staying in Utah in my son's apartment where I had access to skis and kept a few extra personal clothing articles like some undergarments, a hoodie, a pair of docker pants, and a pair of loafer shoes. And I figured I could also borrow other stuff from him if I got desperate. I also had access to a washer/dryer there. but still, I was proud of my cheapskate-self to get by for ten days on just a medium size backpack, which the ski boots took up most of the room.