Can I use someone else's airline miles to book a flight?

Yes, with most major U.S. airlines. Delta SkyMiles, United MileagePlus, American AAdvantage, Southwest Rapid Rewards, and JetBlue TrueBlue all allow you to book flights for other people using your miles. You don't need to be traveling yourself — you can book a ticket in someone else's name with your miles.

The main restriction: you generally can't combine miles from multiple accounts to book a single ticket (though some programs allow transferring miles between accounts for a fee). Each airline's rules differ slightly — some charge a fee for booking award tickets for non-family members, while others (like Southwest and Delta) impose no restrictions at all.

One important caveat: the miles belong to the account holder, and some airlines' terms technically prohibit "selling" miles. So you can gift a flight booked with your miles, but selling your miles or trading them for cash violates most programs' terms of service and can result in account closure. For family travel, many programs also let you pool miles into a shared family account. Check your specific airline's program rules — but the short answer is yes, you can almost always use your miles to book for someone else.