Are their seats the size of Southwest - or smaller?
I can't do SW - shoulders are too wide.
Smaller, less padding and the tray might fit your iPhone.
I disagree on that. I just flew on 2 southwest 737 max 8’s. It’s their newest planes. The seat bottom is angled higher in back. Which means less forward Leg support.
Frontier flies Airbus a320’s. The Airbus is wider which means wider seats by about 7/10ths of an inch. Also frontiers interiors and seats are very spartan very thin padding. However to me they are very comfortable still. Southwest is a great airline but the 737 is dated and needs a total redesign.
2 tips for frontier. Don’t be fooled you can take a carry on back. Just not 2 for free. I travel with a back pack. So I am good. Also don’t pay extra for the seat assignment. Select the very rear of the plane. It’s more likely to have open seats next to you in the back. Plus the seats are free or the cheapest