Perhaps, Ace Combat: Skies of Hostility or Ace Combat: Skies of Fury?
Two trademarks trigger the thought. Namco Bandai registered Skies of Hostility and Skies of Fury in Japan. Both sound related to Ace Combat or maybe Sky Crawlers. We’ll go with Ace Combat since that hasn’t had a sequel in awhile.
While there are two trademarks, Namco Bandai probably isn’t working on two games. They have a habit of registering multiple titles they never use like Broken Curse (an alternate for Soulcalibur: Broken Destiny), Endless Links (Destiny Links) and Tales of Blessia.