For most trips you can only bring one personal item when you're flying in Basic Economy. You can't bring a carry-on bag unless you're flying to South America, across the Atlantic or across the Pacific. All other bags have to be checked.

United Airlines is extremely strict regarding its Basic Economy carry-on policy. Unlike standard Economy, a Basic Economy ticket strictly prohibits a full-sized carry-on bag for the overhead bin; passengers are only allowed one "personal item" that must fit under the seat in front of them (max dimensions 17 x 10 x 9 inches). Gate agents are trained to identify Basic Economy boarding passes and will intercept passengers attempting to bring a larger bag to the gate. If you are caught with a carry-on that doesn't fit the "personal item" criteria, you will be forced to gate-check the bag and pay the standard checked-bag fee plus a $25 gate handling fee. The only exceptions to this rule are for MileagePlus Premier members, Star Alliance Gold members, or those using a qualifying United Credit Card, who are still allowed one full-sized carry-on even when flying on a Basic Economy fare.