THE aircraft disturbance in Ruislip and Eastcote last night was caused by RAF Northolt checking their instrument landing system (ILS).

The light aircraft was brought into the base in West End Road, South Ruislip, to check the system between about 11pm and 3am.

Squadron Leader Richard Willis said: "We have an ILS here so if there's any problems planes can be guided into land and that has to be tested outside the hours Heathrow Airport operates.

"It's an aircraft safety system and it has to be done in the early hours of the morning. It's normally done three or four times a year but we have done it twice in the last few weeks because a new system has been installed. I am not aware of any more plans in the near future but there will have to be one in a few months.

"I understand it's an irritation and we do regret any disturbance to local people but I am afraid it has to be done."