Several airports serving the London business aviation community have called for judicial clarification as to whether RAF Northolt, which encourages business flights to use it on a commercial basis, adheres to the aerodrome safety rules civil airports have to follow.

The request for judicial review was rejected on a technicality, but the judge ruled that the UK Civil Aviation Authority, not the Military Aviation Authority, is responsible for ensuring the safety of civil aircraft that use Northolt. This reverses current assumptions.

The action was initiated soon after the Ministry of Defence was granted permission to extend the cap on annual business aviation movements at Northolt – which is closer to central London than any of the plaintiff's aerodromes – from 7,000 to 12,000.

The airports that filed for a judicial review of Northolt's safety are Biggin Hill and London Oxford. The court dismissed the judicial review, but required the CAA to pay its own costs and issued a judgement on the law: "It is the Secretary of State for Transport/CAA, rather than the Secretary of State for Defence/Ministry of Defence, which has statutory responsibility for safety in relation to the use ofRAF Northolt by civil aircraft."

It adds: "The MAA does not have statutory responsibility for the safety of all aircraft using RAF Northolt. Its safety responsibilities are confined to the safety of military aircraft using RAF Northolt."

The reason for the review's rejection is that "we knocked on the right building but the wrong door", as Biggin Hill's managing director Will Curtis puts it.

The judge says he was asked to rule on whether the government’s arrangements for overseeing and regulating the use of Northolt airport by civil aircraft are lawful, particularly in respect of safety – not on whether RAF Northolt meets appropriate safety standards for such aircraft.

However, according to counsel for Biggin and Oxford, in some respects Northolt does not meet those civil standards, and the judgement says that is the CAA's responsibility – not the MAA's, as the CAA still claims.

Curtis offers two examples involving Northolt aerodrome where the site does not comply with Civil Air Publication 168 and ICAO Annex 14. The runway end safety areas, he says, do not meet safety regulations, and the main runway 25 has a petrol station under its short final approach. The RAF officers' mess – a listed building – also encroaches into the approach path.

The judge says: "These are statutory responsibilities which must be discharged by the [CAA]. They cannot be fulfilled by delegating to the MOD/MAA the task of assessing the safety of RAF Northolt for use by civil aircraft."

Curtis says he has written formally to the CAA and awaits a reply.