The pilot has overall control within a range of about 20-28 degrees, but within those parameters the actual temperature control is left up to the flight crew, who will generally set is at 22 or 23 degrees.
If the temperature drops to 20 degrees passengers start to shiver and complain, but anecdotal advice from flight crew suggests that more passengers faint when the temperature rises above 24 degrees.
This is supported by a study conducted by a study published by the American Society for Testing and Materials, which concluded "There is evidence that cabin pressure and temperature may contribute to the occurrence of syncope", the medical term for fainting.
This results from a deficient blood flow to the brain, which might happen when a passenger rises after a prolonged period of inactivity.
Fainting is more likely to occur following a sedentary spell in an aircraft than at home, sitting in front of the TV for example, because air pressure in the cabin at typical cruising altitude is equivalent to the outside air pressure at 1800–2400m above sea level.
At that altitude, less oxygen is available to be transported in the blood stream, which increases the incidence of fainting.
Flight crew also suggest that passengers sitting in the rear of an aircraft are more susceptible, along with overweight males, elderly passengers and those with cardiovascular conditions.