If you’ve flown a return trip recently you might wander why it took a different amount of time to get to your destination as it did to get home? Sometimes your outbound flight might be significantly longer, or shorter than your inbound flight leaving you questioning why the difference in time? There are many reasons that affect the flight times, but by far the main reason is the chosen route or flightpath taken for that particular flight. Indeed, it may not even be limited to just inbound and outbound flights, you might find that a flight time differs from the same route from the same airline on different days. So why do airlines operate different flights paths for the same route?
Jet streams are narrow bands of fast flowing, westerly air that circulate the globe and play a significant role in determining how long your flight might take. Depending on your route, airlines are likely to use the jet streams to their advantage to fly with a tail wind, or reduce the headwind. At cruising speed, wind direction and speed can have a significant affect on the actual air speed of aircraft. The harder the engines have to work to maintain cruising speed and the longer you are in the air will also result in more fuel / cost for the airline.
Whilst the jet streams are generally reasonably reliable and predictable, localised wind and air pressure could affect a proposed flight route or chosen path on a particular flight. The airline is likely to have a few flight path options available to them for any given route and will optimise their path within air traffic constraints accordingly.
Different airspaces have different sector taxes to fly within and is likely a consideration from the airlines when optimising their flight paths. A slightly longer route may have a significantly lower sector tax and whilst you are likely to use a little more fuel to fly ‘around’ such sectors, the overall cost benefit may still validate avoiding certain airspaces.
Areas of conflict are avoided by airlines when planning flight paths for obvious reasons. Warzones and associated airspace is avoided when planning flight paths and whilst contingencies are made by the airlines and air traffic controllers for high risk zones, conflict can break out at any time and lead to cancellations or short term redirects that could add significant time to your flight. When the Syrian conflict broke out, significant flight delays were common as airlines rushed to avoid flying through its airspace and whilst the region is still in a state of high tension, longer term plans to avoid Syrian airpace are still in place.
The Eyjafjallajökull ash cloud of 2010 affected air traffic across Europe as Iceland’s airspace was engulfed in volcanic ash, which blew across much of northern Europe. Hundreds of flights were cancelled as it was deemed unsafe to fly and where not cancelled many routes were redirected causing significant delay.
For example, flying from New York
directly can take as little as 11 and a half hours, or as much as 13 hours depending on which flight path the airline chose. Similarly, a flight from London Heathrow
can take as little as 3 hours and 45 minutes with a healthy tail wind or as long as 5 hours return, that’s over 25% longer in the air and 25% more fuel being burned.