Malaysia Airliners has confirmed it has lost contact with a Boeing 777 over eastern Ukraine which was enroute from Amsterdam to Kuala Lumpur, flightnumber MH17. Some reports are claiming the aircraft has been shot down while cruising at about 30.000 feet.
Pro-russian seperatists have shot down high flying aircraft before but never machines flying at this altitude, previous shoot downs were on aircraft flying at about 20.000 feet which would put them at the upper edge of man portable air defences.
Reports now emerging are suggesting the system used might be a 9K37 Buk (NATO reporting code SA-11 Gadfly) system captured from Kiev government stock. This system is theoretically capable of downing aircraft operating at 30.000 feet. Nothing is confirmed at the moment though, the crash might be due to other causes.