( CNN ) -- As the world struggles to come to terms with the horror of another passenger jet falling from the skies , the full picture of how and why Malaysia Airlines Flight 17 came down over eastern Ukraine is far from clear . The United States believes a surface-to-air missile brought the Boeing 777 down over territory held by pro-Russian separatists but has n't indicated who 's responsible -- though both sides in the ongoing civil conflict in Ukraine blame each other . According to a top Ukrainian official , the airliner , which was en route to Kuala Lumpur from Amsterdam with nearly 300 people on board , was flying at about 10,000 meters ( nearly 33,000 feet ) over the Donetsk region of eastern Ukraine when the missile hit . A number of airlines have since re-routed services away from the region , prompting questions about whether commercial aircraft should be anywhere near conflict zones anyway . `` Was this an accident waiting to happen for any airliner flying over that part of the Ukraine -- and there were plenty of them ? '' asked CNN aviation expert Richard Quest . `` Although there had been restrictions over Crimea , in this part of Ukraine there are no restrictions . The space between the ground and 32,000 feet had been closed by the Ukrainians . Above 32,000 feet it was open . This plane was not doing anything wrong being where it was . `` We can argue whether restrictions should have been in place with everything going on there , but when that pilot flew that route ... there was nothing wrong with doing so . '' `` That part of Ukraine is essentially ungoverned space , and when you have ungoverned space you have these kinds of calamities , '' said retired U.S. Army major general and CNN military analyst James `` Spider '' Marks . `` Sadly , we should not be surprised by this . '' Russian weapon . `` We do n't know who had their finger on the trigger , but clearly this is Russian kit , whether in Ukrainian hands or in Russian , '' he added . Analysts believe this `` kit '' could be a Buk missile system . Known as the SA-11 among NATO forces , it was developed by the Soviets and operated by both Russian and Ukrainian forces , according to retired Brig . Gen. Kevin Ryan , director of the Defense and Intelligence Project at the Belfer Center for Science and International Affairs at Harvard University . As to where the order came from , Marks suggested air defense units could be operating without central control . `` It could be an independent process , '' he said . `` That means individual operators of that launcher or mobile air defense system can engage targets at will based on certain profiles -- they see an aircraft , its altitude , it does n't transpond in a way they can figure out , so their initial reading is that it 's military and they fire because they have the authority . What you 'd prefer to have is some back-up systems , but that was clearly not the case here . '' Investigation worry . With much of the wreckage believed to be in territory held by separatists near the Russian border , there 's concern that international inspectors may not be granted access to conduct a proper investigation before the crash site is `` contaminated '' or tampered with . `` Ultimately , the international community is going to demand that there is a proper , full investigation , '' said Quest . Matthew L. Wald , a reporter with the New York Times , told CNN it was important to bring in a skilled investigator to look for clues in the wreckage . `` What you look for in a 'shoot down ' or explosion is the condition of the metal . Are there shrapnel holes ? Are their entry wounds and exit wounds -- something that went through the airframe ? Are there bends in the metal characteristic of high explosives ? If someone skilled can find it , they 'll be able to make a diagnosis . '' Cockpit clue . He said the aircraft 's cockpit voice recorder could also provide vital clues if they survived a possible blast . `` You might catch conversations between the crew . This has happened before in airplanes that were shot down , where it 's clear pilots were talking to each other about damage to the plane . They know what 's happened and that would makes things clearer , '' said Wald . `` There 's no reason why we should n't get the recorders , '' added Quest . `` Yes , there was a very violent fire and a very violent crash , but this thing is designed for this . '' Yet it 's by no means certain that outside assistance will be permitted inside such a volatile area . However , Wald says that there is a precedent for data recovery . `` When the Soviets shot down Korean Airlines Flight 007 ( in 1983 ) ... they said they 'd recovered nothing . `` The father of a young college student was on that plane . Hans Ephraimson-Abt went to Moscow , went to ( President ) Gorbachev and brought back the black box -- and that cockpit voice recorder told a lot . '' The friends and relatives of Flight 17 will be hoping they will be spared the anguish of not knowing too .
The United States believes a surface-to-air missile brought Malaysia Airlines jet down . A U.S. official says the plane was shot down, but it is unclear if that happened before or after it entered Malaysian airspace. A number of airlines have since re-routed services away from the Ukraine region . Analysts worry about international inspectors being given access to crash site .