I just packed my Dahon Vybe in the flight for a business trip to Columbus OH. It was a bit of a struggle at first until I removed the rear derailleur. After that things went in pretty smooth thanks to the photos in this thread. Room for the helmet and sneakers with a few spots I can put clothing, just need to watch the weight.

I had to remove the fenders, the derailleur, and one pedal. I used ties to hold the chain on the crank to avoid the chain tangling.

Needed a 15 mm wrench for the wheel bolts and the Allen wrench for the pedal.