The Mainpack is designed to be checked in using the Flight & Rain Cover whilst you take The Daypack on the flight with you.   The Mainpack measures at 63cm in length which puts it slightly bigger than carry-on size for most airlines and especially the low-cost ones. We have taken The Mainpack as a carry ourselves and know customers to do the same, as you are able to squish it down if you under pack it, however we cannot guarantee that you won’t be charged.   Always carefully read the airline’s policy on check-in luggage before you travel.