What is the meaning of 'no-fly zone'?

Explaining 'No-fly zone'

As Qazet.az reporting earlier, Ukraine's President Zelensky has once again called for the West to instate a no-fly zone over Ukraine.

But that has been resisted by Nato. But why ?

A no-fly zone in a war is aimed at stopping aircraft from entering banned airspace, usually to prevent attacks or surveillance.

But such a ban needs to be enforced by military means.

A no-fly zone over Ukraine would mean that military forces (specifically Nato forces) would engage directly with any Russian planes spotted in those skies and shoot at them if necessary.

That would effectively bring Western nations into military combat with Russia, a dramatic escalation to the war.