SUSPECTED MISSILE ATTACK

Diverting planes is expensive for airlines, requiring more fuel and more time in the air and making some reluctant to do so without clear directives.

Flight MH17, en route from Amsterdam to Kuala Lumpur, was flying at around 33,000 feet over eastern Ukraine when it was brought down.

The United States said the plane was probably felled by a ground-launched missile strike, while Australian Prime Minister Tony Abbott said on Friday that Russian-backed rebels were responsible.

Immediately after the incident, several airlines announced that they were re-routing flights to avoid Ukrainian airspace, including Russian carrier Transaero.

As well as criticising some airlines, Dell and other experts said the onus was also on civil aviation regulators to provide clearer directives on avoiding conflict areas.

"The safety authorities themselves have much to answer for," said Chris Yates, of London-based aviation consulting firm Yates Consulting. "This is an information disconnect as well, ultimately."

Ukrainian authorities had closed the flight path from the ground to around 32,000 feet, according to Eurocontrol, the agency responsible for coordinating European airspace. Flight MH17 was flying 1,000 feet above that.

After the crash, the International Air Transport Association (IATA) said that "based on information currently available it is believed that the airspace that the aircraft was traversing was not subject to restrictions".

The Malaysian Airlines executive noted that airlines are guided by advisories from regulators called NOTAMs, or Notices to Airmen, which alert aircraft pilots of potential hazards along a flight route that could affect its safety.

In April, the US Federal Aviation Administration (FAA) issued a NOTAM order prohibiting US aircraft from flying in the airspace over the Crimean region of Ukraine and nearby parts of the Black Sea and Sea of Azov.

That area was expanded in response to events on Thursday.

Some conflict areas pose more of a threat than others.