A Malaysia Airlines Boeing 777-200ER was shot down by a surface-to-air missile system on July 17, according to a U.S. government official.

Ukrainian officials have suggested it was a SA-11, a mobile air defense system.

"We know that a missile was fired. It is uncertain from what exact location," the source says. "The question is, was it [launched from] the far Eastern tip of Ukraine or possibly from Russia."

The radar-guided missile, which the government official says can reach targets at altitudes of up to 80,000 ft., has been described as a "very lethal" threat for allied aviators in the past.

Both Kiev and separatist spokesmen denied they had fired at the aircraft, but the U.S. government source says Washington feels "the Ukrainian government has been exonerated." It is believed that U.S. space-based early ballistic missile warning satellites -- the Defense Support Program and Space-Based Infrared System satellites -- were among the assets detecting the missile launch. The government official suggests allies have “other assets in the region” capable of detecting such a launch.

Malaysia Airlines Flight MH17, a Boeing 777-200ER registered 9M-MRD en route from Amsterdam to Kuala Lumpur, crashed Thursday 30km from the Tamak waypoint, about 50km from the Russia-Ukraine border. There were 283 passengers and 15 crew on board. The flight was operated as a code-sharing service with KLM Royal Dutch Airlines.

The aircraft was cruising at 33,000 ft. and at a speed of 476 knots. It left Amsterdam at 1215 and was due to arrive in Kuala Lumpur at 0600 local time on Friday.

There has been intense fighting in the region between the Ukrainian military and separatists since Russia annexed Crimea in the spring. Two aircraft, an Antonov An-26 and a Sukhoi Su-25, have recently been shot down in the region.

Malaysia’s Prime Minister Najib Razak said Malaysia Airlines will dispatch a special flight to Kiev/Ukraine. He has been told by Ukrainian authorities that the aircraft has been shot down. According to Razak, the aircraft did not make a distress call. U.S. Vice President Joe Biden said that the aircraft was “blown out of the sky.” And the Ukrainian Foreign Minister stated in an interview that his government had proof the aircraft was shot down by pro-Russian separatists.

The Flight Safety Foundation (FSF) stated that “any shoot down of a civilian aircraft operating in fully legal airspace, without any warning or justification, whether mistaken or not, represents a flagrant violation of international law and an irresponsible attack on the safety of international civil aviation.”

Following the crash, pilots have been instructed by Eurocontrol to avoid the region, and flights already airborne are being routed around the area by air traffic control in the region.

According to an earlier Federal Aviation Administration (FAA) statement, U.S. airlines had “voluntarily agreed” not to operate in the airspace near the Russian border. The agency issued a Notice to Airman (NOTAM) on April 3 prohibiting U.S. airline flights over the Crimea and some parts of Ukraine adjacent to the Black Sea and the Sea of Azov. The FAA says the restrictions did not apply for the airspace in which MH17 operated, confirming earlier statements by the International Air Transport Association (IATA).

The Ukrainian authorities told airlines on Monday not to operate between 26,000 ft and 32,000 ft. over Eastern Ukraine. MH17 was flying 1,000 ft. above the restricted airspace.

After the shoot-down on July 17, the FAA expanded its earlier restriction by prohibiting U.S. carriers from flying in the Simferopol and Dnepropetrovsk flight information regions, which together cover the Eastern Ukraine.

Some airlines had previously decided not to fly over Eastern Ukraine. However, during a July 18 press conference, Malaysian authorities claimed that 15 of 16 member airlines from the Association of Asia Pacific Airlines (AAPA) were continuing to use similar routes to MH17, and stressed that it was an approved ICAO route.

The crash of MH17 is the fifth Boeing 777 hull loss, following the March 8 disappearance of Malaysia Airlines flight MH370, which was the fourth. Other hull losses were the Asiana Airlines crash on landing at San Francisco, a British Airways 777-200ER, written off after a landing accident in London in 2008, and an EgyptAir 777-200ER which suffered a cockpit fire in Cairo in 2011.

9M-MRD was delivered to Malaysia Airlines in 1997. The aircraft is understood to be MSN28411.