Clarke first ordered troops to race to get to the airport first - that would have shut the russians out.

Then Clarke ordered troops to block the runways to prevent landings - now since presumably the 200 Russian troop had taken the airport with the intention to use it, you couldn't block the runways without opposition from the Russian troops already there.

Then Clarke managed to close the airspace of neighbouring countries.

As for vladimir's

I don't know how you can "oust" a battalion of 200 men without threatening to fire on them.

you can lay siege to the airport and wait for the battallion to run out of supplies.

Now, this is all very strange considering that NATO and Russia were supposed to be on the same side here.
BBC News | EUROPE | Confrontation over Pristina airport

General Jackson tells the BBC: ''We were [looking at] a possibility....of confrontation with the Russian contingent which seemed to me probably not the right way to start off a relationship with Russians who were going to become part of my command.''

We have met the enemy, and he is us — Pogo