'Securing' skies is a term that has been repeated a lot but in practice it means potentially shooting down Russian aircrafts to 'secure' a corridor.
This would mean a NATO member doing an act of war against Russia _without_ the purpose of defending a NATO member state.
The main argument is where do you draw the line? Why did NATO not provide air support for Georgia in South Ossetia, or for Crimea in 2014 but now does so for Donetsk in 2022?
In my opinion doing so would just give Russian propaganda a stronger argument that NATO is intended on attacking Russia rather than securing it's member states.