The Ukrainian government is closing airports in eastern Ukraine from midnight through 7 am because of the confrontation with Russia.
Ukrainian aviation authorities also have declared some airspace in the east to be “danger areas” because of attempts by Russian aviation authorities to seize control of the airspace.
Ukraine acted after Russia issued a ban on civilian air traffic in airspace over eastern Ukraine.
The announcement Wednesday night establishes buffer zones for traffic controlled by Ukrainian authorities to avoid coming into potentially hazardous conflict with air traffic controlled by Russian authorities.
Last week, Ukrainian aviation officials warned pilots in the region to be on the lookout for Russian authorities trying to take control of the airspace and to only recognise Ukraine's controllers.