IFR Preferred Routes
Source: www.pilotworkshop.com/tips/ifr_planning_routes.htm, Featuring Doug Stewart
There are some other things about the route as well - not only the minimum enroute altitudes and all those kinds of things, but are there any preferred routes? Sometimes we might file a route that looks great to us on paper, but ATC is going to say "You can't get there from here, because that's reserved for jets going into Newark" - and they're the only ones who get that airway.
So how do we find out about those preferred routes? There are a lot of sources for them. In your TERPS, in the Jepps, or - and sometimes these aren't published - calling your local TRACON and asking them. And there's nothing wrong with that because quite often, some of these preferred routes are not published, but they're the only one you're going to get.
An example, if I might, just locally - at Pittsfield, Massachusetts, the air space up to 5,000 feet is controlled by Albany; the air space from 6,000 to 10,000 is controlled by Bradley; and the air space above 10,000 is controlled by Boston Center. However the air space that Albany controls at 5,000 and below only extends about five miles east of Pittsfield.
So if you're in Pittsfield and heading to Boston, you might think that you want to go direct east, but Albany isn't going to let you do that because they've got to see you and identify you before they can pass you off to Bradley, and the only way they can do that - especially if you have a very high performance plane - is to fly westbound first. Now, the only way you're going to find that out is by either calling the TRACON, or by calling someone local at the airport that is familiar with IFR procedures out of that airport. So this goes into part of our prior planning.