On the majority of United Airlines aircraft, the headphone jack is the standard 3.5mm (1/8 inch) single-prong jack, which is the same size found on traditional wired earbuds and older smartphones. This is great news for most travelers, as it means you can use your own high-quality noise-canceling headphones without an adapter. However, on some of United's older wide-body aircraft (like certain Boeing 767s or 777s that haven't been retrofitted), you might still encounter the "old school" two-prong (dual-pin) jack. If you run into a two-prong setup, a single-prong plug will usually still work if you plug it into one of the holes (though you might only get sound in one ear), but it is better to have a cheap airline adapter handy just in case. In 2026, United is also rapidly rolling out Bluetooth connectivity on its new and retrofitted planes (specifically the "United Signature Interior"), allowing you to pair your wireless AirPods or Bose headphones directly to the seatback screen. If you are flying on a newer Boeing 737 MAX or Airbus A321neo, you likely won't need a wire at all, though keeping a 3.5mm cable in your bag is a safe "Plan B."