From the other side, my personal record was 13 seperate incidents of being sick on one flight!
My Observer instructor was kind enough to keep count for me as I fought my way through 2 1/2 hours of chasing ships at 500' over the sea off the coast of Cornwall in the back of a Jetstream with a postage stamp window before doing expanding square searches. My nav cycle was almost a work of art, with leg briefings, turn onto new leg, post turn checks, chunder, radio work then back to leg briefings again and so on.
I left the aircaft utterly drained and holding 3 full sick bags as I ran out of stuff to throw!
My advice in no particular order is,
1. Alcohol within the previous 24 hours can significantly increase the risk of chunder.
2. Smooth flying helps avoid it.
3. Allowing them to fly or follow through on the controls is even better.
4. Make it clear that they are to tell you if they feel ill way before they actually start wreching.
5. Cold fresh air.
6. Stop doing whatever manouever it was which brought on the feeling of sickness and don't return to it if possible.
7. Return to the airfield as, once feeling sick, it will rarely disappear, but can ramp up very quickly indeed.
8. Airsickness is less likely if they have eaten a little while before flying.
9. Get them to look straight out ahead at the horizon when turning/manouevering. Head movement whilst manouevering will lead to full bags.
10. Don't risk it if they say they feel better. Bravado's no use when staring at the inside of a sick bag or wiping chunks off the panel.
11. If they are quiet they are probably suffering.
From a graduate of the RAF School of Aviation Medicine desensitization course!
Obs