The Airhitch® definition of "region" is any geographical area within which the distances separating major air-transportation hubs are less than a day's drive -- or bus- or train-ride; or, within which there are easy, cheap local air-transport links between pairs of major air-transportation hubs.
Thus, for example, New York, Boston, Philadelphia, Baltimore, and Washington, most of which are within 4-5 hours' drive or $25 busrides of each other, constitute the "east coast" or "northeast" Airhitch® region. However, because Montreal, a major air-transport hub from and to which many Airhitchable flights operate, is only about 5 hours from Boston and 8 hours from New York by car, and $45-75 by bus, it is also included in this region. (But because of the frequency of Airhitchable flight-opportunities, Airhitchers are never constrained to go to Montreal from Boston or New York to take a flight, although they well might choose to because of the particular contingent pattern of availability that they are presented with at the time they want to fly. An example of this might be an Airhitcher in Boston, whose objective is to get to Paris, in a situation where all Boston- and New York-to-Paris flights are showing low availability, but Montreal-Paris flights are showing good availability, deciding to take the bus or drive to Montreal in order to take advantage of a high-availability, direct flight to Paris.)
On the other side of the Atlantic, the Airhitch® definition of "region" is such that all of western Europe is treated as a single region, since (with the special exception of Greece, which is part of political western Europe and thus Airhitchable) the land-mass it occupies is equal to the geographical area of only one-third of the U.S.: it is approximately as far from Berlin to Madrid as it is from Boston to St. Louis; and since the rail and bus interconnections -- and even AIR interconnections, see, e.g., www.attitudetravel.com -- within the region are so frequent and inexpensive that you can move virtually at will from one part of western Europe to another, on short notice, with no advance planning and at relatively low expense. Further, a very high percentage (some years, as high as 90%) of flights that turn out to be Airhitchable operate into or out of what is known as the "Airhitch® Central Circle" -- a circle of 300 mi. radius with Brussels at its center.
Q. WHAT ARE MY CHANCES OF GETTING THE SPECIFIC DEPARTURE CITY AND/OR DESTINATION I WANT?