Commercial air transport (CAT)

The cost sharing legislation cited here doesn't include a statutory definition of CAT, but the CAA's guidance summarises it:

A flight for the transport of passengers, for which remuneration (payment) or other valuable consideration has been made, is defined as a Commercial Air Transport (CAT) flight.

That is CAP 1590 (guidance), para 4. Para 5 sets out the consequence: "If a flight is CAT or PT, the operator must have an Air Operator’s Certificate (AOC); the pilot must hold at least a Commercial Pilot’s Licence (CPL); and the aircraft must be certificated and maintained in accordance with the appropriate airworthiness requirements."

A cost-shared flight is one that would otherwise be CAT but is allowed to be flown under the non-commercial rules because it meets the conditions in Article 6(4a)(a) and NCO.GEN.102. Fail any condition, for example by taking more than an equal share of the direct costs from passengers, and the flight is treated as CAT again.

CAT is also the benchmark for the safety warning: NCO.GEN.102(f) requires passengers to be "clearly advised that the flight does not meet the same safety standards as a Commercial Air Transport (CAT) flight." Under ANO 2016, the equivalent concept for non-Part-21 aircraft is public transport.