The Federal Aviation Administration classes Mali as a potentially hostile region.
"Civil aircraft operating into, out of, within or over Mali are at risk of encountering insurgent small arms fire, rocket-propelled grenades, rocket and mortar fire, and anti-aircraft fire, to include shoulder-fired man-portable air defense systems (MANPADS)," the FAA said in a notice. Any U.S. aircraft flying below 24,000 feet "must obtain current threat information" and comply with all FAA regulations.
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Flight plans are drawn up by airlines and pilots and submitted to air traffic controllers for approval. Ultimately, pilots fly the agreed routing – unless they receive or request adjustments from air traffic controllers while en route.
David Gleave, an aviation expert at Britain's Loughborough University, described the MD-83 as a "pretty solid airplane in general." He added: "It flies fairly simply, pilots understand how it flies so it is a solid, reliable workhorse … it is unlikely to be the flight crew didn't understand the aircraft."
Gleave said that a variety of problems might be behind the plane's disappearance — potentially ranging from maintenance issues to human error. "It could be something as mundane as multiple vulture strikes," he added.
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Crashes involving Malaysia Airlines alone have sent this year's death toll in aviation disasters beyond the annual global average, according to figures from the International Air Transport Association. The downing of MH17 and March 8 disappearance of MH370 account for 537 deaths – higher than the five-year worldwide average total of 517.
A TransAsia flight also crash-landed on a Taiwanese island Wednesday, killing 48 people.
—By Alastair Jamieson and Jason Cumming, NBC News