The typical size limit for airline carry-on baggae is 22" x 14" x 9". The only folder I know that comes close to that is the Sinclair A-Bike, and it's really a few inches long.

Are there any other bikes that fold down to that size?

I ran a thread on this topic a few weeks ago. Yes, there are such bikes and I had replys from people who had stored bikes in the overhead compartment. Bit more of a problem since 9/11.

Search under: Airplane carry-on folder

http://www.treehugger.com/files/2007/03/thats_one_weird.php

If only it were manufactured.