U

• ultimate load
• ultra-light aircraft
• ultra high frequency
• UN number
• unaccompanied baggage
• uncertainty phase
• unclaimed baggage
• under command
• under way
• underslung
• underwater locator beacon
• unidentified baggage
• uniform
• unit load device
• universal postal union
• universal precaution kit
• unlading
• unlawful interference
• unlawful seizure of aircraft
• unmanned aerial vehicle
• unmanned aircraft
• unmanned aircraft system
• unmanned free balloon
• unpaved runway edge marker
• unruly passengers
• unserviceable
• updraft
• upset training
• upwind
• usability factor
• useful load