Domanda 21, Communication - PPL(A) English - Private Pilot License (Aircraft)

Concerning the safety of an aircraft, a watercraft or some other vehicle or person in sight.
Sent by a pilot or an aircraft operating agency which have an imminent meaning for aircraft in flight.
Concerning aircraft and their passengers which face a grave and imminent threat and require immediate assistance.
Concerning the operation or maintenance of facilities which are important for the safety and regularity of flight operations.