This all went down on a Frontier Airlines jet traveling from Houston to Denver, but the flight had to stop off in Dallas after the troubled passenger started wailing like her leg was cut off ... stirring a huge disturbance.

Nobody seems to know what exactly was wrong with her -- but this video shows her crying and arguing with the in-flight crew and other passengers as she tries getting back to her seat.

At one point ... she even climbs over seats, crawling her way through the cabin, all while sobbing and hyperventilating. As this is all unfolding, some other lady who was in the mix turns to the others and proclaims they're all witnessing a demonic possession.

Describing the passenger losing it, the woman yells, "That's not her, she's possessed! She needs help!" She then goes into preacher mode, telling everyone onboard they need a relationship with Jesus to stave off this sort of "takeover" of the soul.

We can't speak to anything the Holy Ghost did, but we know police immediately boarded the plane when it landed in Dallas to remove the disturbed woman. No one was injured, but it sure freaked out the cabin.

We'll say this, her crawling over the seats definitely brings Linda Blair's horrifying role to mind -- minus the vomit and head-spinning, of course.

Holiday travel ... never a boring moment!!!