Meg, I think what happened with your cat was a fluke. Kidney failure is a sign of feline leukemia or feline infectious peritonis (which one of my cats died from at the age of five.) I would still recommend a light sedative for the flight. Vets know what they're talking about.
I'm sorry; I misspoke. She actually died of liver failure, not kidney failure; one of our other beloved kitties died of kidney failure a number of years ago, not Bella.
Cause of death aside, Bella spent the entire day of the flight foaming at the mouth, panting desperately, and vomiting. She'd never exhibited those signs before. Even if the sedative didn't lead directly to her death, the experience did. I wouldn't wish that on anyone.
The fact of the matter is that most, if not all, airlines will not accept a pet that has been sedated for an international flight. Most, if not all, of the pets brought across by folks on these boards were not sedated, and all (as far as I know) made the journey just fine. There's no need to intentionally disorient an animal who's already going to be confused at what's going on.
*shrugs* Just my two cents. The OP is perfectly capable of making her own decisions, and hasn't mentioned anything about sedatives one way or the other.