In my past experience, Chase customer service will push very hard against any sort of manual adjustment to Freedom categories, but if pushed hard enough (asking once, and then a second time, both via the online secure message center has done it for me) they may be willing to give the missing 4x points as a goodwill gesture.
That could actually work in your favor here, because those goodwill points are credited separately from the transaction itself and thus don't count toward your $1500 of spending cap per quarter, so you could end up getting the 5x points per dollar on more than $1500 of spend per card for the quarter, if you have other planned spending within this quarter's bonus categories.
That said, I also wouldn't go making any big airfare purchases counting on being able to get the goodwill points credited in the first place, and I especially wouldn't count on getting the goodwill points for a second round of airfare purchases after getting them on a first round.