"Sketchup Free and Pro are quite good and have a very "free flowing" build style.  The Pro is $500.00 and the Free version has a proprietary  file format -( a quick google search and I found a few "obj" exporter plugins). - excellent for architecture "

the Free exports to COLLADA. has done since version 7.1.

Airport security is a burden we must all shoulder. Do your part, and please grope yourself in advance.