I have experienced very severe sinus pain on a flight twice in my life. Once on a US Airways flight into DC (maybe 15+ years ago) and then on a Finnair flight from LHR to HEL (in 2000).

The sharp pain struck above my right eye, inside underneath my eyebrow. The pain was so intense, it felt like someone was taking a knife and stabbing me there. I thought my eye would pop out! All I could do was grasp my eye and wriggle in pain. It was awful! Even after landing, the pain did not subside for a few hours, and at that point turned more numb, not completely clearing up until I woke up the next morning.

Still to this day, and after talking with several medical professionals, I am not clear what caused this (or how to avoid it in the future). I've obviously flown many, many flights since then and have never experienced the problem since. I often get paranoid when I feel even the slightest pressure in that area and immediately pop a sinus-congestion pill. Clearly, it is not an experience I wish to relive.

Has anyone else experienced something like this?