Some patients are so scared that they begin to cry even before the needle touches the skin, and they might subjectively be in great pain, but it's not due to the technique itself.
You can read a little bit more about the pain here: http://sci-hub.cc/10.1177/1460408611430175
If I were the FAA, rather than issue drills to flight attendants, I'd focus on perhaps preventing at-risk people from boarding aircraft in the first place. Or train cabin crews to identify situations before they need the in-flight crash cart.
I used to take allergy shots as a child, and was greatly surprised to discover how much less it hurt to stick myself than to have a nurse do it - obviously not because of any better technique (I was eight), but rather because, controlling for noxious stimulus, you experience less pain when you're the one applying it to yourself.
I have no real idea why this is, but would guess it might be related on the one hand to having less bandwidth free to experience pain because you need to concentrate on what you're doing, and on the other hand being in control of what's going on to a greater extent than in the case where someone else is doing it to you. I also have no real idea of how to find studies corroborating the anecdote in a more systematic way, but I strongly suspect they exist and hope someone here will do a better job digging them out of PubMed than I have.
In any case, if it's a choice between having an intraosseous needle or dying, well, bring on the drill! I still have a few things left to do in this life. But I've had broken bones, too, and the pain from such an injury is unique and astonishing in a way that leaves me in no doubt of how unpleasant an intraosseous needle would be.