Police and BAA are recruiting aviation enthusiasts to help fight terrorism at London's Heathrow Airport.
Scotland Yard said the scheme was part of its ongoing security operation
Plane-spotters will be given identity cards and a code of conduct encouraging them to report anything suspicious.
Scotland Yard is backing the scheme, which has been introduced by aviation enthusiasts' club LAAS International.
"Aviation enthusiasts are watching the activities of the airport every day and their legitimate interest can only be to our advantage," a spokesman said.
Ch Supt Jerry Savill, borough commander for Heathrow, said the enthusiasts might be able to recognise people outside the aviation enthusiast community whose interest in the airport was not genuine.
"We want to encourage everyone, but particularly those who know the workings of the airport and can therefore spot something out of the ordinary, to contact police if they believe something they see or hear is suspicious," he said.
Steve Dickens, airport security manager at Heathrow, said aviation enthusiasts could help keep airports secure by reporting suspicious behaviour.
He added: "We also want to ensure that genuine enthusiasts are still able to enjoy their hobby despite extra security measures which are introduced from time to time."
The code of conduct, which spotters agree to when they sign up for the card, commits them to reporting unusual activity as well as clearing up litter and keeping away from security fences.
David Seex, chairman of LAAS International said: "The scheme recognizes that, far from being classed as possible security risks who need to be moved on from car parks and viewing spots in and around airports, genuine aviation enthusiasts can actually play a valuable part in the battle against crime and terrorism."
He said the club had developed the "Aviation Enthusiasts Security Scheme" in response to a request from the authorities for a single sponsoring organisation for plane spotters.
But Mr Seex said the £15 card was available to all enthusiasts, whether or not they were LAAS members.
He said the card would help airport operators "identify the real, responsible enthusiasts".
"When it is launched, we intend it to have the widest circulation amongst police forces and airfield operators, first in the UK and then overseas," said Mr Seex.
The Metropolitan Police has also issued a series of leaflets and posters targeted at aviation enthusiasts as well as airport staff and drivers urging people to report suspicious activity to the anti-terrorist hotline or to local officers.
It said the campaign was part of an ongoing counter terrorism strategy and was not in response to a specific threat.
Ch Supt Savill said: "Police, together with BAA and airlines are working hard every day to help make the airport more secure and the groups we have targeted are in positions, through their work or leisure, which could make them invaluable to our efforts. "
He added: "Experience has shown us that communities defeat terrorism. "