In air travel, a stop or transfer (from one airplane to another) is considered to be a layover or connection up to a certain maximum allowed connecting time, while a so-called stopover is a substantially longer break in the flight itinerary. The maximum time depends on many variables, but for most U.S. and Canadian itineraries, it is 4 hours, and for most international itineraries (including any domestic stops), it is 24 hours. In general, layovers are cheaper than stopovers, because notionally layovers are incidental to traveling between two other points, whereas stopovers are among the traveler's destinations.[3][4][5]