The Russian armed forces do not have control of or indeed the ability to control Kyiv’s airspace. They spectacularly failed to take the city in their first assault and even at that time were unable to gain air superiority. Since then they have retreated out of AA and artillery range of Kyiv, and the reported S-series air defense batteries defending the capital have increased. Simply put, Russia has no real say over who goes to Kyiv. Ukraine is a big country, and they have been beaten back to frontlines that are quite far from Kyiv.
The several posts here which imply the Russians are choosing not to interfere grant them more military competence than they have demonstrated - and are ignorant of the war’s present geography.