The Amsterdam-Kuala Lumpur Malaysia Airlines flight MH17, which was brought down by a surface-to-air missile, flew over Ukraine despite warnings for international airlines to avoid the war zone issued some three months ago, according to aviation experts.

However, the route near or via the Ukraine airspace has been one of the busiest with about 300 flights per day. Airlines flying from Europe to Asian destinations such as Singapore and Malaysia prefer the route because it is the quickest.

In a report in the Daily Telegraph, Norman Shanks, a former head of group security at airports group BAA opined: "Malaysia Airlines, like a number of other carriers, has been continuing to use it because it is a shorter route, which means less fuel and therefore less money."

A number of airlines continued to fly over Ukraine, but at a safe altitude, despite high-level warnings. Immediately after the crash on 17 July, four more airliners followed the same path and did not re-route. The flights belonged to Singapore Airlines, Emirates, Kazakhstan Airlines and Etihad.

In addition, operators believed that they were at a sufficient altitude not to be at risk of attack, and continued to cross the battle-hit region, the newspaper added. The Malaysian Airlines jet was reportedly flying at an altitude of about 33,000 feet, which is regarded as completely safe in the industry.

"The belief was that a plane could not be shot down at that altitude, which is why aircraft continue to fly over zones that have wars going on," an industry source told the newspaper.

Following the incident, Virgin Atlantic said it had diverted a small number of flights, while Turkish Airlines said all of its flights would now avoid Ukrainian airspace.

Airlines including Alitalia, Lufthansa, Air France and Russian carriers Aeroflot and Transaero also diverted their flights.