You and @jonny5
are not grasping the nuances .
First, the US and many nations already provide arms to Ukraine - that isn't "escalation", its a reality. In the cold war that is what all the powers did, supply client states with arms BUT not combat troops. In Vietnam, the Soviet Union and China were well aware that while they could ship the North Vietnamese whatever arms they wished, they could not send Soviet or Chinese troops to engage in combat with Americans...not without provoking an actual war between the powers.
Second, Ukraine is a sovereign state. This isn't an issue of three or four factions engaged in a civil war, with great powers providing troops to influence the outcome. This is a full war of aggression by one state against another sovereign state. "Escalation" is a meaningless term if one side is fighting to obtain full conquest and the other is fighting for its survival. These are not measured responses; the war is already 'all out'.
This isn't any different than WWII. In 1940 the UK was not "escalating" the war, it was fighting for its survival. The US became the "arsenal of democracy", the country that would ship supplies and arms to keep the UK from losing. Same here.
Third, the planes can be shipped in by having Ukrainian pilots pick them up and deliver them. The Russians do not have the ability to seal off the Western and Southern borders, so most of them can be delivered.
Even Putin understands that he would be escalating to threaten direct military confrontation with western aircraft and western pilots...so do we. He might go nuke if NATO troops invade Ukraine, but he will have to live with anything less.