U
- ULD load position
- ultimate load
- ultra high frequency
- ultralight aircraft
- ultralight vehicle
- UN number
- unaccompanied baggage
- unanticipated yaw
- unchecked baggage
- unclaimed baggage
- undercarriage
- underload
- undershoot
- underslung
- underspeed condition
- underwater locator beacon
- undesired aircraft state
- unfeather
- unidentified baggage
- uniform
- unit load device
- universal access transceiver
- universal postal union
- universal precaution kit
- universal time
- universal time coordinated
- unknown state of acclimatisation
- unlading
- unlawful interference
- unlawful seizure of aircraft
- unloading
- unmanned aerial vehicle
- unmanned aircraft
- unmanned aircraft system
- unmanned free balloon
- unpaved runway edge marker
- unruly passenger
- unsealed cowling
- unstable approach
- up current
- updraft
- updraught
- upper-air chart
- upper-air observation
- upper-air sounding
- upper-level chart
- upset prevention and recovery
- upwind
- upwind leg
- usability factor
- useful load
- user charge