It's not just sending jets though. If they arrive in penny packet numbers, Western jets are going to do very little in the overall scheme of things.
Given Russian air superiority, air surveillance capabilities, aircraft reserves and the VERY dense SAM network covering occupied Ukraine, nothing short of a full scale air campaign - a la Desert Storm - is going to give the Ukranians control of their skies.
If you give Ukraine a few squadrons worth of F-16s, all they're going to be really useful for is fighter bomber roles at NoE altitudes. Anything at higher altitudes is going to have to occur WAY behind the front lines, or risk meeting a lot of supersonic telegraph poles. The Russians have too many fighters backed up by AWACs and too many long range SAMs to risk using Western fighters as anything other than ground pounders or drone/cruise missile chasers.
If it was my money, I'd be plumping for more SPAAGs, and medium and long range SAMs. With a new Russian air campaign reportedly in the works, a couple dozen fresh AA systems could play havoc.