I'm going to say that planes shipped to a particular place were packed for that particular cruise, I doubt a plane packed to be shipped on board a sea going vessel woulod be properly packed to withstand almost 70 years in a super wet, high humidity evironment, even if it was under sand. And I seriously doubt that with Japanese occupation looming, folks are going to figure out the vast logistics involved and the sheer manpower,planning, time and equipment needed to do that when in reality they were merely thinking about their next meal and how to evade, escape, and survive Japanese occupation. Again, hard to believe that they would expend that much effort towards the end of the war when Allied victory was eminent to pack, dig, bury and then keep secret for almost 70 years planes that were for all intents and puposes scrap. A few well place hand grenades would have accomplished rendering them useless to the Japanese anyhow if keeping them from being captured was the intent.