Malaysia Airlines MH17 airliner apparently shot down over rebel-held eastern Ukraine was flying over airspace that a number of other Asian carriers abandoned months ago because of security concerns.
South Korea's two main airlines, Korean Air and Asiana, as well as Australia's Qantas and Taiwan's China Airlines said they had all rerouted flights from as early as the beginning of March when Russian troops moved into Crimea.
"We stopped flying over Ukraine because of safety concerns," Asiana spokeswoman Lee Hyo-Min said.
Korean Air re-routed its flights 250 kilometres (160 miles) south of Ukraine from March 3 "due to the political unrest in the region", an official for the carrier said.
A Qantas spokeswoman said its London to Dubai service used to fly over Ukraine, but the route was changed "several months ago", while Taiwan's China Airlines diverted its flights from April 3.
Quizzed as to why Malaysia Airlines had not taken similar precautions, Malaysian Prime Minister Najib Razak said international air authorities had deemed the flight path secure.
"The aircraft's flight route was declared safe by the International Civil Aviation Organisation. And (the) International Air Transportation Association has stated that the airspace the aircraft was traversing was not subject to restrictions," he said.
Re-routing would have involved a longer flight-time and therefore higher fuel costs.
Singapore Airlines said in a statement that it had been using Ukrainian airspace but had "re-routed all our flights" to alternative corridors away from the region.
It was not immediately clear when the route change was put into affect.
Hong Kong's Cathay Pacific said it had not been using Ukrainian airspace "for quite some time".
According to the European flight safety body Eurocontrol, the Ukrainian authorities declared the east of the country a no-fly zone shortly after the Malaysian airliner went down with 298 people on board.
European and US airlines rerouted their flights as Kiev said flight MH17 was shot down in a "terrorist" attack and a US official said intelligence analysts "strongly believe" it was downed by a surface-to-air missile.
"Since the crash, the Ukrainian authorities have informed Eurocontrol of the closure of routes from the ground to unlimited (altitude) in Eastern Ukraine," Eurocontrol said in a statement.