MH17: It's 'normal' to fly over conflict zones
Airlines have now imposed a no-fly zone over Ukraine as questions grew over they were in the first place, given it has been three months since pilots were warned to avoid it.
At least one Kiwi is feared dead and 27 Australians are among 298 people killed when a Malaysia Airlines jet flying from Amsterdam to Kuala Lumpur was shot down over Ukraine.
Ukrainian authorities had now closed all routes, diverting about 300 flights per day. Delays are likely.
Airlines had kept flying across the Ukraine to save money, Aviation specialist Norman Shanks said.
"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."
Flights for Singapore Airlines, Emirates, Kazakhstan Airlines and Etihad followed the route, even after the crash.
Air New Zealand said it had no flights across the Ukraine.
Airliners had continued use the route as they felt they were at a sufficient altitude not be shot down.
It is "perfectly normal" for commercial airlines to fly over conflict zone, a New Zealand aviation expert based in Geneva says.
The plane was brought down by a Buk ground-to-air missile and is the fourth to be shot down in that area in the past week.
Pro-Russian separatists took a Buk system last month, but it was not reported whether the theft was from the Russian or Ukrainian militaries.
The United States Federal Aviation Administration warned US aircraft in April not to fly over part of Crimea, the disputed area between Russia and Ukraine.
The no-go zone did not include the area where Malaysia Airlines flight MH 17 crashed this morning , about 322km away.
It was not unusual to fly at an increased height over countries experiencing civil conflict that was "not a fully blown war", Aviation Advocacy founder and chief executive officer Andrew Charlton told Radio New Zealand.
Air New Zealand had flown over conflict zones such as Afghanistan and Iraq en route to London "for many years", Charlton said.
Airlines made decisions about where to fly based on factors such as the wind and other flight plan, he said.
It was only after MH17 crashed in Ukraine this morning that other airlines tweeted to say they had changed their policies and would not fly over the country, he said.
If an aircraft was travelling at an altitude of 10,000 metres, only "remarkably sophisticated weaponry" could bring it down, he said.
The Buk ground-to-air missile launchers possessed by Ukrainian government and pro-Russia separatist forces had a range that could hit an aircraft at this height, but it would require "fine marksmanship" to hit a plane travelling at 900kmh and would be a deliberate act, he said.
That the commercial aircraft had been mistaken for a military one could not be ruled out, he said.
There was no way for the plane to signal its status, as civilian and military aviators operated on different systems, he said.
Airlines had already filed their flight plans for the day, and would have to contact and divert their flights that were underway, he said.
The Ukraine was under a "very common flight path" for flying from Europe to Southeast Asia, and aircraft would be diverted south in the coming days, which may increase flight time and fuel useage, depending on the wind, he said.