Last week you may have noticed strange planes flying over Luxembourg.

These are in fact NATO surveillance aircraft, known as AWACS (Airborne Warning and Control System), and Station.lu reported them about six months ago.  Last week they were back in Luxembourg airspace and seemed to be constantly circling the Grand Duchy. 

They are also used as spy planes but as they were so evident, they were obviously not on a mission!

The aircraft were extremely easy to spot with the most striking feature being the huge radar disc on the rear, reminiscent at first sight, of a flying saucer.

These planes have been spotted several times in the past few months over Luxembourg and last week, notably Thursday, they flew a dozen times over the Grand Duchy.

The offices where Station.lu is located in Hamm is in the direct flight path for Luxembourg Airport and it looked as though these AWACS planes were rehearsing approaches takeoffs and landings.  We counted them passing overhead at least a dozen times, and of course, took the opportunity to snap a few photos.

The usual use of this special type of Boeing is to fly at an altitude of about 9500 metres.  From this height surveillance with a range of up to 400 kilometres, can monitor aircraft and ships below, including locating and identifying enemy aircraft.