User blog comment:FairyRaven/Fairy Tail Chapter 400: Wings of Hope, Review and Commentary/@comment-2214433-20140913105601/@comment-9595671-20140913110311

Yeah, if the dragons are inside them its because they're older than 80 they couldn't pass. Worse possible way a dragon's longevity could backfire. If only Freed had known so he could have used that enchantment to stop Acnologia from chasing them.