Amid the many changes airlines are making to combat rising fuel costs, including cutting routes and increasing ticket prices , there's one particular change that might make you reconsider the way you pack. Major U.S. airlines like JetBlue, American, United, and Delta have recently raised their checked bag fees, most now charging $45 for your first piece of luggage. As a travel writer who flies monthly, I’ve witnessed firsthand how often checked baggage rules change, which is why I use this one travel hack as much as possible to save money: carry-on backpacks. Typically sized as personal items, these bags are lightweight, spacious, easy to carry, and can essentially function as a second carry-on— if you pack them strategically.   Travel + Leisure editors have tested 96 carry-on backpacks , and I’ve included several of our favorites on this list, as well as pilot-approved picks from Samsonite , Cotopaxi , and more.…