This backpack is a perfect size to use as a carry-or daypack.  I had enough room to put everything I would need for a flight and when I put it under the seat in front of me I still had a bit of leg room.  I also used it as we went sight seeing which allowed me to put a tour book and any souvenirs we bought but not to big to walk around the stores with it on your back and knock things over.  It is well made and I felt secure with it on my back because of the interlocking zippers.  I would highly recommend.