Quote Originally Posted by SephirothNL
Only thing I found there was Hades-Materia.
We're told that the plane was carrying weapons and equipment to be used in the fight against Sephiroth. It seems that Shinra was planning to invade the Northern Crater; the Gelnika was helping to carry supplies for that plan. The Hades Materia isn't the only powerful item there; you can also find Yuffie's ultimate weapon, the Conformer, and the 'Highwind' manual for Cid's ultimate limit break... amongst other things. That plane is loaded. It also had a miniature Mako reactor on board; the monsters roaming the plane are experiemental creatures, perhaps being developed for use as weapons.