At the very least, NATO would declare anything in the air within a few hundred miles of a NATO border to be a valid target, since they'd then have to assume it'

At the very least, NATO would declare anything in the air within a few hundred miles of a NATO border to be a valid target, since they'd then have to assume it's a threat of attack against a NATO state. Instant de-facto no-fly zone over much of Ukraine. No way Russia's gonna do that, since even that kind of minimal response would be disastrous for them.