Perhaps you frequently fly between a city pair and noticed that the type of aircraft you fly on changes from time to time, or the amount of time spent in flight varies significantly. Let’s discuss just a few of the many considerations airlines make when dispatching aircraft on a particular route.

Route planning

Flight times are elastic, and dispatchers do their best to make them as short as possible. Perhaps the most significant factor for route planning is whether your route of flight will expose your plane to a headwind or tailwind. When at cruise altitude, “jet streams” are largely responsible for determining this. At risk of oversimplifying it, jet streams are rivers of air that always move from west to east. They move significantly closer to the equator during the winter months. Right now in the Northern Hemisphere, the jet streams are stronger and closer to the equator, while in the Southern Hemisphere they are weaker and closer to the South Pole. This means that in the Northern Hemisphere, most aircraft are exposed to stronger headwinds or tailwinds (depending on the direction of flight).

If you flew a round trip from London to New York, you would notice that the return flight to London has a shorter time en route regardless of the season. Remember, the jet streams always move easterly. But during the autumn and winter months, you will also notice that the difference between flight times increases. The westbound journey becomes longer while the eastbound journey shortens because the jet streams have strengthened and moved closer towards the equator—much further south, in this example. A congruent example for the Southern Hemisphere would be a trip from Johannesburg to Sydney. The eastbound trip from Johannesburg to Sydney would be shorter in the winter months (June-September) and the westbound journey would be longer when compared to the summer months.

Dispatchers attempt to plan the cruise portion of flights with the most advantageous winds.

Photo: Getty Images

Dispatchers pay close attention to where jet streams are and how fast the air inside of them is moving. Flight routes, especially long-haul routes, are modified daily to take advantage of the most favorable tailwinds or avoid the most degrading headwinds. On international flights, dispatchers also consider “overflight fees.” Countries charge foreign air carriers for the right to transit their airspace and utilize air traffic control services. Most countries charge per mile, so dispatchers use highly advanced software to calculate the potential costs of higher overflight fees against the cost of burning more fuel whilst flying a less-efficient route to avoid them. It’s a very fine balance that makes a significant impact on the profitability, and thus feasibility, of an airline’s long-haul strategy.

Once airborne, pilots might be given an “en-route re-route.” An example of a smaller re-route would be a change to an arrival procedure due to the winds at the airport necessitating takeoffs and landings change directions. This kind of re-route would add only a few extra miles and result in very little time difference. A more significant re-route might be encountered if a block of airspace were to close. This could happen if military exercises are scheduled, if there is a volcanic eruption, or, more likely, if unsuitable weather conditions exist (such as a thunderstorm).

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A thunderstorm, which would require circumnavigation, as seen from the air.

Aircraft selection

It’s fairly intuitive that with more demand for a given route will come larger aircraft and more available seats. Of equal concern to airline management is the kind of tickets that are in demand. In particular, the amount of premium cabin seats that are in demand for a route influences which aircraft is deployed. First, business, and premium economy class sales are one of the largest influencers for profitability. Without taking into consideration other factors, airlines would rather accept a high “load factor” in premium cabins with a lower percentage of the total seats filled compared to a higher overall load factor with a smaller proportion of premium seats sold.

Examples of various travel classes on Delta Air Lines

Photo: Getty Images

Interestingly, some smaller aircraft have more premium seats that their larger counterparts. United Airlines and American Airlines both offer 12 business seats on the Embraer E175 compared to the eight available on the larger Airbus A319. All things being equal, this makes the Embraer jet more proportionally profitable. A higher frequency of smaller aircraft allows the airline to fill more seats while simultaneously offering more departure time options to passengers, which has shown to be of value to the consumer. It’s not that simple though–the airline has to consider the cost of additional crews, baggage handlers, hotel rooms, gate fees, and so many other variables.

American Eagle Embraer E175

Photo: Vincenzo Pace | Simple Flying

Another significant influencer for the type of aircraft you will be flying on is the city pair itself. In the United States, some airline hub cities serve as “crew bases” for only part of the airline’s fleet of aircraft. Flight attendants can generally fly on an entire fleet, while pilots are restricted to their type rating. This means that you are less likely to fly on an aircraft that does not have pilots for a particular aircraft originating and finishing trips in that city.

A particularity that you might observe in the United States is the increased deployment of wide-body aircraft on domestic routes during the winter. If you fly Delta Air Lines or United Airlines, you stand a chance to fly on a Boeing wide-body when you travel between the East and West coast any time of the year. This is due to demand, as well as the length of the journey. During the Holiday travel season (which we are entering into the thick of), you might also find that your flight between a closer city pair of hub airports is being served by a larger aircraft. With international demand down during the winter, airlines use their larger planes in the most economical way. This means deploying them on hub-to-hub operations, or to increase potential load factors to destinations with warmer climates.

These examples are only a small sample of the myriad of considerations airlines make. Aircraft selection and route planning are at the forefront of what makes airlines viable businesses. What makes this topic so interesting is how dynamic it is. Then again, the same could be said about the entire aviation industry.


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