When I was in the RAF I was onboard a Lockheed L1011 Tristar coming back from the Falklands after a 4 month tour during the 90's. We were flying along the west coast of Africa when the fasten seatbelt sign came on. This was just in time as we ran into some severe turbulence and the kite was being thrown around all over the place. The worst part was when everyone had that sensation when you leave your stomach behind when you drop and it turned out afterwards that we lost 500 feet in altitude. Everyone was bricking it and I thought my number was up but we eventually got through it and climb back to our assigned altitude. That was a couple of very scary minutes that seemed to drag on forever and luckily nobody was injured although quite a few sick bags were used up.