Herman de Wulf/BRUSSELS

David Learmount/LONDON

A NORTHWEST AIRLINES McDonnell Douglas DC-10-40 carrying 241 passengers from Detroit to Frankfurt missed its intended destination by 300km (160nm), landing at Brussels Airport by mistake on 5 September.

The pilots of Flight 52 only realised their error when they lined the aircraft up for the approach at Brussels. In spite of that, they decided to land anyway.

The pilots apparently were the only people unaware of the unplanned detour. Puzzled cabin crew and passengers had been following progress on the live map display in the cabin.

Although the flight was not at put at risk, the US Federal Aviation Authority has set up a full inquiry into the incident, and Northwest Airlines has suspended the pilots from duty.

Early reports from Brussels air traffic control (ATC) attributed the original error to Shannon ATC, alleging that an incorrect code had been entered into the aircraft's ATC flight-plan data, re-designating the aircraft's destination as Brussels.

The Irish Aviation Authority denies this, saying that the crew had acknowledged its destination as Frankfurt, and that the correct data was passed to the London Air Traffic Control Centre, the last such centre before Brussels.

By the time the aircraft entered the Brussels control region, however, its destination had been re-designated, Brussels ATC maintains. The UK National Air Traffic Services declines to comment, as the event is under investigation.

The aircraft's planned track for Frankfurt would normally have taken it over Belgium at its cruising altitude of 37,000ft (11,300m), according to ATC conditions. The upper-airspace (above 24,500ft) over Belgium, however, is handled by the Maastricht ATCC in the Netherlands.

A senior Brussels ATC official confirms that the aircraft was cleared by the LATCC as it left the London control region to descend to 24,000ft and contact Brussels. The crew started the descent and called Brussels on the assigned frequency, addressing the controller as "Frankfurt" and announcing its intention to land.

Brussels did not question the addressing error which, Northwest says, occurred more than once in subsequent transmissions.

Brussels approach instructed the crew to descend in-bound via Bruno, a Vor navigation beacon on one of the standard approaches to Brussels Airport. The crew had to ask ATC for the Vor's frequency. The aircraft was subsequently cleared for an instrument-landing system (ILS) approach to Brussels' runway 25L, which is the same runway orientation as at Frankfurt, but with different ILS frequencies.

At some point the crew finally realised they were landing at the wrong airport and opted to continue the landing for safety reasons, says Northwest. The airline has said that, whatever errors ATC may have made, if any, the crew must "share responsibility" for what happened.

Source: Flight International