I've traveled to Alaska (eagles) with my 500mm f/4L several times, and ill return this fall as well. I use a Pelican 1510 case: http://www.pelican.com/cases_detail.php?Case=1510
I do not use the dividers, just the top foam and the padding on the sides and bottom. I cut a slot in the foam top to avoid pressure on the lens cap. I found the dividers unnecessary as I filled the case with other equipment: lenses and bodies.
Read the airline websites on their size and weight limits for carry-ons. This case works for domestic flights, but some international flights have tighter restrictions. With what I carry, I'm right at 40 pounds.
This makes rolling through airports a breeze, but not so much fun carrying it down a trail. If that is where you are heading, consider the The Gura Gear Kiboko or whatever they have these days.