is this too big to use as a carry on bag for a plane?

I just got back from using this bag on multiple international and domestic flights, and I would say that this bag is too big to be used as a carry on for any flight. The detachable bag is small and can easily be used as a carry on, but the main bag is much too big, especially since you cannot zip the carrying straps into the bag with this bag (also something to remember when checking the bag - the shoulder straps remain exposed whereas some bags allow you to zip a cover around the straps and turn the bag into a duffel so the straps aren't caught or destroyed).

kim, It depends on a few things. First of all, every airline has their own requirements, generally listed on websites, so check the requirements for the airlines you're most likely to use. Keep in mind that there are weight restrictions too. Having said that, based on the limits for Air Canada, NWA, American Airlines, and Qantas, this bag's too big. You might get away with the 65L on British Airways, but it's borderline. If you're planning on flying on anything other than major routes that might get a smaller aircraft, there's a good chance it just won't fit anywhere you try to put it. Of course, if you're only going to half fill it and then cinch it down to be smaller, then it might work. If you're looking for something that you want to try to carry on but don't mind checking, then by all means try. If you're looking for a bag that you can count on being able to carry on, go smaller. Probably something 3000 cu in (50L) or less.