The punctuality of flights has improved on a global scale in the last few years, despite the growing number of passengers, departures and arrivals. Thanks to clever algorithms and improved hardware, all processes on the apron, on the runway and within the terminal are planned and organized in an intelligent, efficient and proactive way to provide on-time performance. Still, delays are happening. They are not only annoying for passengers but extremely expensive for the carriers, with compensation costs being only the minor share of the total. Flight delays and cancellation cost airlines globally $30 billion a year in lost revenue, in addition to costs borne by their passengers.
To put the cost factor aside for a moment: what’s more annoying from the passenger’s point of view? If your flight departs late or if it arrives late? What’s the big difference, one could say? If it departs late, it will most certainly arrive late anyway. Once an aircraft has lifted, the arrival time is pretty much set unless it will take a detour for whatever reason and collect even more delay. Is there a difference? Are arrivals more delayed in average than departures or vice versa? What is actually a delay and when is there a chance to still meet all OTP-related deadlines and Service Level Agreements (SLA)? According to the European Organization for the Safety of Air Navigation (EUROCONTROL) and the US-American FAA (Federal Aviation Administration), a delay is defined as a deviation from the planned off-block time of more than 15 minutes.
If an aircraft lifts off with a delay of another 5 minutes – which means 20 minutes altogether – it is likely to catch up the delay, depending on the wind and the total duration of the flight. This is reflected in the official statistics: On average, the calculated delay on arrival is slightly less than that on departure – 4.2 minutes less in 2017. Of course, this is an average and this figure will vary significantly between pairs of airports (and even more so for individual flights). For airport pairs (such as Frankfurt-Madrid flights or Amsterdam-Lisbon flights), actual average gate-to-gate times typically range from about 15 minutes less than the scheduled time to about 5 minutes more.
Tailwind Support for Record
Assuming that these numbers are true, and the flights are more punctual on arrival than on departure, it can only mean that the aircraft will try to make up for lost time during the flight, even if it is only a few minutes. However, this of course depends very much on the flight duration. At a planned flight time of 45 minutes, it is difficult to make up again – goodbye, punctuality and OTP. The situation is different for medium and long-haul flights: Los Angeles to Hawaii, Frankfurt to the Canary Islands, New York to London. A new record was recently set for the latter route: on February 9, 2020, a Boeing 747 made it in 4:56 hours. The aircraft reached a top speed of 901 miles an hour. Due to the extremely favorable tail wind, the pilot could have made up for a delay of more than two hours.
Of course, that was just extremely lucky and usually is not the case. But the example shows how much could be caught up in the air – at least theoretically. On the contrary, headwinds can cause even more delays or force the aircraft to increase the engine performance and thus use more fuel.
These circumstances are of course already considered in the flight plans. They usually apply to all long-haul flights in an easterly direction. For instance, flights from Europe to the Caribbean are calculated around an hour shorter than the other way around.
Fuel largest Single Cost Item
When looking at the total costs of a flight, it shows that fuel is the largest single cost item, even at low fuel prices. Subsequently, increasing the travel speed costs money due to higher fuel consumption. Airlines only spend it as an investment to avoid even higher costs, for example to avoid downtime or compensation costs.
In their normal daily business, airlines have different options to reduce fuel consumption of their overall fleets: Buy new aircraft with a lower average fuel consumption, change technology onboard the aircraft or change the way the aircraft is flown. We will concentrate on the latter one – to be precise, saving fuel during the so-called cruise phase. This refers to the segment of every flight after climb and before descent. Airline flights spend significant amounts of time in the cruise phase. In domestic US operations, about 56% of total flight time is spent in cruise. For an airplane carrying some amount of weight, there is one speed that minimized fuel burn, depending in different factors like aircraft type, configuration, occupancy level and so on. If aircraft flew exactly the same path over the ground but sped up or slowed down to an optimal speed, the total fuel consumption for each flight would be lower on each flight.
Slower Flying reduces Costs
So slower flying reduces flight costs. For exactly this reason, flights on the same route surprisingly take longer today than in the 1970s. Airlines have identified a slower pace as a big lever for fuel savings. For example, one of the major US carriers, Southwest, estimated it saved almost $ 27 million by adding only one to three minutes to each flight.
Recent research found that stage lengths centered on 1500–2000 miles have the lowest fuel burn rates under current technology, fleet composition, and seat configuration. Additionally, European studies found that the aircraft’s fuel consumption per passenger and 100 flown kilometers decreases rapidly with range, until a near constant level is reached around the aircraft’s average range. At longer range, where payload reduction becomes necessary, fuel consumption increases significantly. It shows that saving fuel costs is a science in itself. Nevertheless, it’s not only about economic constraints or OTP achievements, which are a major concern for every single airline. At the level of a global society, it is also an ecological problem. Higher fuel consumption also means ever higher emissions – a fact that the aviation industry must face. Worldwide there is a growing awareness of more sustainable business practices and travelling. As long as no truly sustainable and emission-neutral flights are possible, the aviation industry must ensure that it pollutes the environment as little as possible.