Does this include commercial flights? All of the commercial flights I have tracked via flighaware (admittedly only a handful) seem to take less direct routes. Is this direct routing only available to GA aircraft?
Well, not really. Officially, according to the FAA, a Cessna 172 with GPS, a CitationJet with GPS, a CRJ-900 with 2 GPSs, and a B-747-400 with INS/etc all have exactly the same priority when it comes to IFR. Now with that being said, let's bring common sense/common operating practices in:
Example 1: when I fly AUS-JFK my company files for, and we get cleared for a route that takes us due eastbound across the Southeast US, over ATL, to pick up the east coast into NYC. Not exactly a direct route, is it? That is an FAA preferred route that joins up into 1 of the 3 major routes into JFK. We could file direct if we wanted, but we sure ain't gonna get it. They have routes between most major cities of the US so 2 aircraft going between the same cities will fly exactly the same route and stay in line. Thats also the reason for SIDs and STARs. They organize the traffic into a few easy to manage flows to get in to/out of the terminal areas. Some SIDs/STARs are bettter and more useful than others (compare a SID/STAR from ATL or CVG vs SID/STAR from JFK or LGA).
Example 2: Let's say you wanted to fly a Bonanza between 2 smalleror medium airports, for example BDL-ALB (Hartford, CT to Albany, NY). You can file for, and most likely will receive a direct routing. You won't get in the way of any major traffic streams across the US.
Example 3: I used to fly a CitationJet 525, based out of HAO (Hamilton, Ohio, a GA/corporate reliever airport for Cincinnati). We frequently flew down to Naples, FL where the company owner had a house. We would file direct to CVG-V97-HYK then direct (Cincinnati VOR, victor airway to Lexington, KY, then direct down to FL). That was to satisfy the requirement to stay out of the CVG terminal area (yes, that routing is more directly through the CVG airpspace rather than overall direct route, but it was used to vector us around the area).
So, moral of the story is: Anyone can file direct routing. But only if you won't conflict with a major traffic stream.
