Professor Peter Vink of  TU Delft’s faculty of industrial design engineering, discusses the challenge of finding the correct cabin temperature

Sixty-eight per cent of passengers report a poor experience related to the temperature on an aircraft, according to a survey of 900 flyers conducted by Tapis in 2023.

Sometimes, it is experienced as too cold by passengers, sometimes as too warm. While mostly experienced in mid-flight, entering an aircraft with no air conditioning can also lead to discomfort.

When it is hot outside, the aircraft is often even warmer; when it is freezing, the aircraft can be very cold.

Differences

Research shows that humans are not capable of defining the absolute value of temperature.

Human sensors are good at noticing differences but not absolute values. A draught is immediately felt, but a slow change is not.

A 2008 study by Kolarik showed that if you increase the temperature 0.6 degrees Celsius every hour in an office for four hours, people do not feel it.

At a certain point, people get too warm or too hot and they start noticing it although there is a range where humans do not complain about the temperature.

Individual

When humans are active, a lower environmental temperature is preferred. When they are passive, they need a higher temperature to feel comfortable.

That means that in an aircraft, the temperature can be relatively high, between 21-25 degrees Celsius.

Of course, it also depends on clothing and if you have a blanket or not. Some airlines even turn the temperature down to sell more blankets.

Preference over temperature differs therefore not only according to activity but also between people. This means that personalisation of temperature is a way to achieve improved comfort ratings.

A blanket, a shawl or a passenger service unit (PSU) making a cooling breeze can allow the passenger to have some influence over temperature.

This is important as it gives a feeling of control, independent of what other passengers prefer.

One of the difficulties in a cabin is that passengers are passive, thus requiring a higher temperature, while flight attendants are active and so requiring a lower temperature.

The flight attendant’s perception might be that it is too hot and they might adapt the temperature according to their perception or ask the pilot to change the temperature, which could make it too cold for the passenger.

Head/feet

Research has shown that for good sleep, humans need warm feet and a cool head. In an aircraft, it is mostly cold at feet level and warm at head height.

Solving this is not easy as warm air usually rises. In some aircraft there are heated floors in the galleys, which are appreciated by flight attendants.

It is however not easy to implement heated floors throughout the whole cabin as airflow is needed to let air pass through HEPA filters.

These are needed to clean the air and have become especially important in Covid times.

Modern aircraft like the Boeing 787 and A350 have better temperature regulation, which should lead to less passenger complaints so, in the future, complaints about temperature might be reduced.

However, there is always the human factor. The fact that busy cabin crew control the temperature could lead to too high or too low temperatures.