The category "<flight_id-not_creatable>" can be expressed as follows:

<flight_id-not_creatable>

<flight_noun> of <digit-pl> <specific_aircraft_type-pl>

<flight_noun> of <specific_aircraft_type-pl>

<flight_type-not_creatable>

<flight_type-pl> <id_num-pl>

<flight_type-sing> <id_num-sing>

<ordinal-pl> <flight_type-pl>

<ordinal-sing> <flight_type-sing>