The Sky Train looks and feels smaller than the Air Boss but technically the Sky Train has 156 more cubic inches than the Air Boss. (20 x 9 x 13 vs. 21 x 8 x 13) Both, however, can easily be overpacked and bulging and be too heavy. If you have to pack up to the limit and heavy the Sky Train is easier to use since it has a backpack option which is very helpful in most travel situations.

I've been on some trips where I squeezed a briefcase into the Skytrain to comply with an unexpected 1 bag requirement on a flight. I've been on others where I packed very light and only had to use the main compartment of the Skytrain. It is very versatile.

If you feel like splurging you can get a Western Flyer for your 1-3 day trips and then use a Skytrain or Air Boss for the longer ones. Even if you are an extreme light packer like me you would appreciate the available extra room on the Skytrain if you needed it. With luggage compression straps (available from Red Oxx) the Skytrain will compress to a small size but still look very good.