The Federal Aviation Administration (FAA) had warned U.S. airlines about flying over Ukraine, where a Malaysia Airlines plane was downed on Thursday.
Malaysia Airlines confirmed that it "lost contact" with a flight that crashed near the disputed area of Ukraine that has been occupied by Russian military forces since the spring.
The FAA prohibited U.S. airlines from flying near the area when the dispute over the territory first began in April.
"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.
Ukrainian officials have alleged that the Malaysia Air flight was shot down by Russian separatists.
The FAA said Thursday afternoon that the Malaysia Air flight that crashed was not operating in the specific airspace that was included in its April 3 warning.
The agency said it was "monitoring the situation to determine whether further guidance is necessary."
"The FAA was in contact with U.S. carriers following the crash of Malaysian Air Flight 17," the FAA said in a statement. "The agency confirms that carriers have voluntarily agreed not operate in the airspace near the Russian-Ukraine border."
State Department spokeswoman Jen Psaki said during a briefing on Thursday that the department can’t confirm reports about casualties or the cause of the crash.
Malaysia Air officials said the plane was carrying 280 passengers and 15 crew members after departing from Amsterdam.
"Malaysia Airlines confirms it received notification from Ukrainian ATC that it had lost contact with flight MH17 at 1415 (GMT) at 30km from Tamak waypoint, approximately 50km from the Russia-Ukraine border," the airline said in a statement.
"Flight MH17 operated on a Boeing 777 departed Amsterdam at 12.15pm (Amsterdam local time) and was estimated to arrive at Kuala Lumpur International Airport at 6.10 am (Malaysia local time) the next day," it added.
The incident follows the disappearance of a Malaysia Airlines flight that prompted a prolonged multinational search earlier this year.
The first missing plane, Malaysia Air 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 still not been found, baffling both lawmakers and aviation officials.
— Rebecca Shabad contributed to this report.
This story was updated at 3:57 p.m.