I am watching the #TwilightZone 1959 episode "Nightmare at 20,000 Feet". As with William Shatner's character, I too had hallucinations on a plane. The irony is that he is offered a sleeping pill AFTER his hallucination, and I took a sleeping pill BEFORE my hallucination.
I didn't hallucinate monsters, I tripped literally balls of neon colours ricocheting against each other on the cabin's ceiling. I flew Cathay Pacific: the staff translated my prescription and assigned me a personal attendant.