I can only speak for US travel with long lenses.
I long ago ditched the hard cases for trips, relying on a camera pack instead. The cases are simply too heavy and bulky, plus they are inconvenient to carrry on hikes through terminals. My pack is a Tamrac 787, but there are lots of other worthy ones. I rearrange/remove the internal dividers to suit my needs trip by trip. Worst case, I carry both my 500 f/4 and 300 f/2.8 at the same time, along with a body and smaller lenses in the 787. Additional gear and my laptop goes into a Tamrac Photo Messenger bag.
I've never had beef from any US airline about the load, but I'm careful about overall dimensions. I have no doubt that they wouldn't like the weight, but I'm also careful not to act like it's heavy so that no one is inspired to look closer.