Weather, cost determine which routes airlines fly
Question: Take two cities where the destination is the same distance whether the plane travels east or west. How does an airline decide which route to take?
— Todd Frederick, Wheat Ridge, Colo.
Answer: Often there is preferred routing provided by air-traffic control to help smooth the traffic flow. Otherwise, the most efficient route, taking into account winds and turbulence forecasts, is filed.
Q: How do you choose the route to use from point A to point B?
— Daniel Boies, USA
A: The flight plan routing is chosen for the minimum flight time while avoiding bad weather and restricted airspace. Air-traffic control reviews the flight plan and may modify it for traffic separation needs.
Q: Why would a route from India to the USA fly over the U.K. and not China or Australia?
— Dipesh Mehta, India
A: The airline’s flight dispatch office will look at the most efficient route. The selection of the route can include the mileage, wind and cost of overflight permits.
Based on these criteria, the answer to your question would be because it is the most cost-efficient.
Q: When flying from New Zealand to the south of Chile, there is a very short route (polar route), but it seems not to be used. Why not?
— Theodor, Sweden
A: Due to the remoteness of the route and the lack of alternate airports, only specially qualified airplanes can use them. These airplanes and the certification process are expensive; the demand does not justify the expense.
Q: When flying a great circle route, i.e. Stockholm to New York, how do pilots or navigation systems adjust for the constant change in compass course?
— Doug, Stockholm
A: Modern flight management systems fly from waypoint to waypoint. It is done by the flight-management computer.
Q: When flying, how much discretion is given to pilots when deciding which way to go, and the appropriate flight path? Is it all done via computer on the ground? How about certain airlines/countries that do not want their airplanes to be flying over certain places for political reasons?
— Steve, New York
A: Flight plans are filed with air-traffic control. If there is a reason to avoid an area, it is stated in the flight plan. Pilots receive clearance from air-traffic control and fly that clearance. If there is a reason to change the route, pilots request an amended clearance. Air-traffic control will approve the amendment unless there is a traffic conflict.