On Thursday, November 28, 2013 10:19:45 AM UTC+13, Nightjar wrote:
On 27/11/2013 20:36, Matty F wrote:
... And why not have a few columns inside to hold the roof up instead of
huge expensive trusses that can fall down?

Columns constrain how you can lay out the area and nobody knows what
sort of layout might be needed a few decades from now.

It's just an airport where people wander around aimlessly. No particular layout is needed. It's not like a stadium where the columns might obscure the view of some ball game. It's not like a building here that has lots of planes in it, many of them hanging from the ceiling, so they have an excuse for having a high ceiling with no obstructions.
Supermarkets have lots of columns and that's no problem. They might even allow a garden to be put on top of the roof one day!