Direct flights between Ukraine and Russia will stop on Sunday, as new sanctions initiated by Kiev come into effect.
Moscow first called Kiev's ban on Russian airlines "madness", then announced that it would mirror the move.
Ukraine now says flights will end at midnight on Saturday, after last-minute crisis talks failed.
Up to 70,000 passengers a month will be affected.
The sanctions are intended to punish Russia for annexing Crimea and supporting armed rebels in eastern Ukraine. The fact that they have been introduced now, when a ceasefire is finally holding on the ground, shows how bitter relations remain.
