comments:
https://www.amazon.com/dp/B07B7G22FF It’s just a bit under the max dimensions, which means a you can overfill it a bit, and it has straps to compress it down if needed. It also perfectly fits a 16” MacBook Pro.
This pack was recommended because it fits within Frontier's required dimensions, has straps, appears durable, and is well priced. I purchased one and will be testing it in three days. I'll report back. It looks really good so far.https://www.amazon.com/dp/B07B7G22FF?psc=1&ref=ppx_yo2ov_dt_b_product_detailsBtw this topic is in several other threads already so reading them will give you additional good ideas. Reporting back I used the bag for several flight segments and the bag fit loosely in the sizer. No issue. More fits in it than I expected. Better quality and more solid than I expected. A full change of clothes + toiletries in case I was stranded plus a rolled up heavier pack for when I arrived at the destination plus snacks and two computers. It's fine for a day pack with water and snacks but if you're actually hiking I recommend something more heavy-duty.