The warning from the British Airline Pilots' Association comes as the runway at Gatwick Airport was closed for parts of Sunday evening over fears for safety.
Four EasyJet flights were diverted and one British Airways service was sent to Bournemouth Airport following the closure, while other flights circled the West Sussex airport.
BALPA is calling for compulsory registration of drone users to allow police to track down people flying them irresponsibly.
The union's flight safety specialist, Steve Landells, said: "Yet another incident at Gatwick involving drones shows that the threat of drones being flown near manned-aircraft must be addressed before we see a disaster.
"Drones can be great fun, and have huge commercial potential, but with a significant increase in near-misses in recent years it seems not everyone who is flying them either know or care about the rules that are in place for good reason.
"We believe a collision, particularly with a helicopter, has the potential be catastrophic."
He added that as the number of drones being sold takes off, new technology should be looked at to address safety concerns.
