Ukraine closed its airspace to civilian flights on Thursday while Europe's aviation regulator warned airlines against flying commercial planes over neighboring countries, citing a high risk to safety.
The European Union Aviation Safety Agency also recommended that operators “exercise caution” over large parts of Russia after President Vladimir Putin ordered a large-scale military attack in the Ukraine.
Moldova also closed its airspace for all flights and Belarus shut part of theirs due to the Ukrainian crisis.
"There is a risk of both intentional targeting and misidentification of civil aircraft," the European regulator said. "The presence and possible use of a wide range of ground and airborne warfare systems poses a high risk for civil flights operating at all altitudes and flight levels."
EASE urged operators to “exercise caution” when flying in airspace controlled by Moscow and Rostov-on-Don in Russia “due to heightened military activity which may include launches of mid-range missiles penetrating into controlled airspace.”
In 2014, Malaysian Airline flight MH17 was en route to Kuala Lumpur from Amsterdam, when it was downed by a Russian-made Bulk missile over Eastern Ukraine. Russia has denied any involvement in the crash that killed 298 passengers and crew members. Dutch investigators concluded the Boeing 777 was hit by a surface-to-air missile supplied to pro-Russian separatist rebels in Donetsk, one of two separatist-held areas recognized by Putin as independent this week in a prelude to the invasion.
This is a live update. Click here for complete coverage of the crisis in Ukraine.