China's Air Defense Zone

I see the US has flown 2x B52's over the disputed islands

Japan has responded by announcing the Chinese declaration is not valid & 2 of its airlines are not implementing the new Chinese rules for its aircraft routing.

Are we going to need a sequel to "Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb"?

These kind of 'measures' are often extra legal and unfounded under public international law. Every aircraft, be them state, commercial or private enjoy full freedom of navigation over high seas (int'l airspace) which is practically the area beyond the territorial waters unless of course they're hijacked or exploited as pirate craft.

The PRC seems to have unilaterally declared ADIZ to especially annoy/thwart the Japanese mil aircraft patrolling in and around that zone. Their government advisers reportedly said that they might be flexible in operating the zone vis a vis the third party state aircraft. So the PRC's 'new measure' aims mostly at state aircraft. However one state cannot enforce or coerce any state aircraft to submit flight plans, disclose other info or re-route them which are flying in int'l airspace beyond its territory. This is a well known and established int'l customary practice that is also widely accepted in the relevant jurisprudence. If the states that are not at war or close to state of war try to liberally bend this practice/principle, they would be simply regarded as unfriendly-churlish to down right belligerent. And such unwarranted attempts are again often foiled or challenged by some states  that attach paramount import to upholding the freedom of navigation around the globe.

As known, this issue stems from the Diaoyu/Senkaku sovereignty dispute between China and Japan and related clashing maritime jurisdiction area claims. Territorial and sovereignty issues are the hardest to overcome. Most obvious resolutions, in traditional sense, resorting to use of force or knocking on the door of the Court (ICJ). Another maybe more palatable option could be co-establishment of a joint development/exploitation zone enclaving those islands/islets as well as adjacent maritime areas until a peaceful and comprehensive settlement can be attained.

Evaluating the developments in their context, it would have been totally biased to only blame the PRC as the Japanese are not sitting duck, so to speak. Both sides of the conflict have been willfully playing the game of upmanship since the issue has become a reheated thorny matter more than a year ago. As usual again under these kind of situations both governments test each other and the int'l community while each time providing domestic consumption with something to chew on. Therefore, the PRC's ADIZ should be seen as a part of a controlled escalation plan which would most likely be responded in kind by Japan. Yet escalation being a quite sharp tool may easily slip out of hand. Prolonging the confrontation is neither good for both countries nor for peace and stability in the region and the world economy.

As we all say in our business, may the cool heads prevail !