Airlines are avoiding flying over Ukraine after a Malaysia Airlines plane crashed in the country, and may have been shot down.
"Out of an abundance of caution, Delta is not routing flights through Ukrainian airspace and is monitoring the situation involving Malaysia Airlines Flight 17," Delta said in a statement.
Dutch airline KLM, which shares flight codes with Malaysia Airlines, also said it was avoiding Ukraine airspace.
"Although not yet officially confirmed by Malaysia Airlines, it is with great regret that KLM has learnt about the possible incident with flight MH17, codeshare KL4103, of Malaysia Airlines from Amsterdam to Kuala Lumpur," the Neatherlands-based airline said in a statement.
"We are in contact with Malaysia Airlines to obtain further information," the KLM statement continued. "As a precautionary measure KLM avoids flying over the concerned territory."
The Federal Aviation Administration (FAA) had warned U.S. airlines about flying over Ukraine in April, when a dispute over the country's shared border with Russia first began.
"Due to the potential for conflicting Air Traffic Control (ATC) instructions from Ukrainian and Russian authorities and for the related potential misidentification of civil aircraft, United States (U.S.) flight operations are prohibited until further notice in the airspace over Crimea, the Black Sea, and the Sea of Azov," the agency said in an April 3 notice.
Malaysia Airlines officials have said the plane that crashed was carrying 280 passengers and 15 crew members after departing from Amsterdam.
Ukrainian officials have alleged that the flight was shot down by Russian separatists who have been battling Kiev.
The incident follows the disappearance of a Malaysia Airlines flight that prompted a prolonged multinational search earlier this year.
The first missing plane, Malaysia Airlines Flight 370, disappeared from air traffic control radars about an hour into its flight from Kuala Lumpur, Malaysia, to Beijing in March. That plane, which was carrying 239 passengers, has yet to be found, baffling lawmakers and aviation officials alike.
-This story was updated with new information at 4:32 p.m.