DW: A passenger plane has crashed in Ukraine, apparently shot down. The Boeing 777 was flying at a normal cruising altitude of over 10,000 meters. How likely is it that an aircraft can be shot down at such a height?

Heinrich Grossbongardt: This is very unusual. Although rebel and guerrilla groups have shoulder-mounted anti-aircraft missiles, these are relatively small caliber, such as Stinger missiles, which have a maximum ceiling of 3,000 to 4,000 meters. To get to 10,000 meters requires much different hardware. And that's something rebel organizations did not have access to in the past.

In recent weeks, there have been numerous incidents of arcraft being shot down over the conflict zone in eastern Ukraine. Yet passenger aircraft continued to fly over the area. Was the high altitude sufficiently safe?

According to previous experience, it was considered safe. The Ukrainian military planes that were shot down all flew far lower. Civilian air traffic over Ukraine remained unaffected the entire time.

Until now, major arms suppliers - whether Americans or Russians - have paid very close attention to ensure that anti-aircraft missiles that could endanger commercial aircraft are not delivered to resistance groups. If the rebels were responsible, it will be necessary to find out how they could come into possession of such a weapon.

Some US airlines stopped flying over eastern Ukraine in April. Was it not negligent of other airlines to continue to fly there?

No, it wasn't negligent. Although the US Transportation Safety Authority may have issued a warning, responsibility for European airspace rests with the European air safety authority, which has many years of experience.

Until now, transport aircraft at cruising altitude have only been shot at by the military, such as Korean Air Lines Flight 007 in 1983 or the Iran Air Airbus A300 over the Persian Gulf five years later, which was shot down by an American frigate. Armies have such weapons, but so far no rebel organizations.

What chance does a pilot in a passenger aircraft have to recognize a missile attack?

No chance at all. Only military aircraft and those carrying vulnerable people such as heads of state have equipment to warn against rocket attacks. Commercial aircraft do not have such systems on board.

Do missiles fly so fast as to make evasive measures futile?

Yes, that would be pointless. Commercial aircraft are relatively sluggish.

Does pilot training cover the possibility of these attacks happening, such as during take-off or landing?

After 9/11 this was a big issue. It's also an issue when we fly to especially vulnerable airports such as Kabul or Baghdad, where there have been attacks. There, they certainly use special takeoff and landing techniques to reduce the risk.

Heinrich Grossbongardt is an aviation expert with Expairtise Communications in Hamburg.