Legally, there is no weight limit for passengers on commercial flights in the U.S. In general, obese passengers on airlines who require a seatbelt extender and/or cannot lower the armrests between seats are asked to pay for a second seat on their flight, unless there are two empty seats together somewhere on the plane.

Overweight passengers can certainly fly, but as of January 2026, several airlines have implemented stricter "Customer of Size" policies. Southwest Airlines, for example, transitioned to assigned seating and now requires passengers who cannot fit between the armrests to purchase a second seat in advance, with refunds only granted if the flight is not sold out. Most major carriers like Delta, United, and American Airlines follow a "encroachment" rule: if a passenger cannot lower both armrests or spills into the adjacent seat, they may be required to purchase an additional seat or be rebooked on a later flight with more space. Seat belt extenders are provided free of charge on almost all flights to ensure safety. To avoid stress at the gate, many plus-size travelers now proactively book two seats or seek out airlines with the most accommodating reputations, as the "free extra seat" policies of the past have largely been phased out.