Asked why Malaysia Airlines had not taken similar precautions, Prime Minister Najib Razak said international air authorities had deemed the flight path secure.
"The International Air Transportation Association has stated that the airspace the aircraft was traversing was not subject to restrictions," he said.
According to the European flight safety body Eurocontrol, the doomed plane was flying at a level known as "330", or approximately 10,000 metres or 33,000 feet.
The route had been closed to level "320" but was cleared for those flying at the Malaysian plane's altitude.
European and US airlines re-routed 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.
Analysts were divided on whether carriers like Malaysian Airlines had been negligent in opting to continue flying over Ukraine.
"I just find it astonishing. I am absolutely flabbergasted," said Geoff Dell, an air safety expert from the University of Central Queensland in Australia, told Sky News.
"If there's trouble spots on the globe, then you take a decision to avoid that area," Dell told Sky News.
"You don't put your primary assets -- your passengers, your crew, your airplane -- at risk unnecessarily," he added.