Does anyone know why EasyJet uses U2 as the prefix for flight numbers? Other airlines have more logical prefixes. Eg. KL -> KLM, AZ -> Alitalia, BA-> British Airways, etc. Even though they do not always match the airline name exactly, they do mimic the name.
EZY (EasyJet UK) code and EZS (EasyJet Switzerland)are the ICAO codes, whereas U2 is the code generated by IATA for them when they applied for an IATA code.
EasyJet Airline Company Limited (UK Based) - (IATA code: U2; ICAO code: EZY; Callsign: Easy) EasyJet Switzerland SA (IATA code: DS; ICAO code: EZS; Callsign: TOPSWISS)
ICAO codes are used for operational purposes like flight planning, ATC, etc. IATA codes like U2 are generally used in timetables, reservation systems, departure/arrival information, etc. - in other words information that is meant for the general public.