I have used my Think Tank Airport Addicted backpack to haul my 400f2.8, Gitzo Monopod, 3 1D series bodies, 8 spare batteries, 70-200f2.8, 16-35f2.8, 1.4x, 28-70f2.8, laptop and other random 'crap' all over the place.
The biggest hick-up is getting dinged for oversize/over weight outside the United States for carrying it on (American Airlines dinged me 3 times in the US at DFW back in 2005 and refused to let it go on as carry on........I have flown roughly 1,000,000 miles since 2005, less than 5,000 miles of it on American Airlines, or any One World Alliance airline, since the triple carry on denial)