It’s summer time, so why is it so cold on airplanes?

As up to 100,000 people a day travel through Dublin airport in summer, we answer this and other travel questions

With between 90,000 and 100,000 of us passing through Dublin Airport and taking to the skies every day during the summer months, so we thought it was time to answer some nagging air travel questions that we mull over every time we board a plane…

Why is it so hot and then so cold on a plane?

The topic of airplane cabin temperature hit the headlines this summer when a woman on a United Airlines flight from Denver complained that her infant son overheated and passed out while they sat on the tarmac for almost two hours during a heat wave. In Rome, passengers had to disembark an Alitalia flight after a similar stint on the tarmac. In a statement, a spokesman for Alitalia, Paolo Sanguinetti, said the plane's captain decided to disembark passengers because he "did not get authorisation by air traffic control to start the aircraft engines in order to cool the cabin". And this is why the temperature on a plane goes from sweat-inducing highs as you board to Arctic-cool mid-flight: the air conditioning units are generally turned off to save fuel before the plane is in the air. Some larger, heavier planes need the power that is drawn away by air conditioning units for take-off, which is why they are not turned on until after the aircraft has ascended to a suitable altitude. This means the body heat of passengers getting settled on board heats the cabin quickly and temperatures soar.

Mid-flight, however, the chill sets in. Aircraft temperatures are generally kept at between 22 and 24 degrees, which is about the same air temperature of most office environments. The extremes of the range reach from 18 to 27 degrees. What makes it feel cooler than the office is that most passengers don't move around during a flight meaning they don't work up any body heat of their own. This leads to the overwhelming sense of cold. So should the cabin temperature not be increased to counter this? In short, no. A study conducted by ASTM International, a global standards organisation, found that more people are likely to faint in a warm cabin, owing to hypoxia, a medical condition common in airline passengers that occurs when body tissue does not receive enough oxygen. According to Airbus, "the heat given off by passengers in a fully occupied cabin is considerable. Incoming air needs to be at or below the required cabin temperature if that temperature is to be maintained".


But before you reach for your airline blanket, you might be interested to know many airlines re-use their blankets without washing them, so you might want to avoid it unless it is sealed to avoid other passengers’ germs.

Anyone for ice?

While on the subject of germs, did you ever wonder why you can no loner get a glass of water on board most planes? Well, an Environmental Protection Agency (EPA) study in 2004 found that out of 327 aircraft's water supplies, only 15 per cent passed health standards and one in every 10 of the samples tested positive for coliform, an indicator that other potentially harmful bacteria may be in the water. In 2009, the EPA created the Aircraft Drinking Rule Act and since then most planes don't serve drinking water from the tap. It's worth remembering that ice on board is still made using the same water supplies, so you might want to skip it. Tea and coffee is also brewed using on-board water and even boiling doesn't typically reach hot enough temperatures to kill E. coli, according to the EPA.

Can you make airplane food taste better?

On a more positive note, though airplane food is rarely inspiring – despite investment by airlines in celebrity chefs – there are ways to make it taste better. The reasons it doesn’t always tickle our taste buds is not just down to the pre-cooking processes. At high altitudes our taste buds actually don’t work properly. Low humidity dries out our nasal passages and air pressure desensitises our taste buds. But as well as the altitude, loud engine noise also contributes to our inability to taste and smell food on board.

A study published in the food journal, Food Quality and Preference found that loud noise impacted our perception of taste. Forty-eight diners were blindfolded and fed sweet foods and salty foods while listening to silence or noise through headphones. The study found that loud noise led to less acute sense of the sweetness and saltiness of the foods. Charles Spence, professor of experimental psychology at Oxford University, says the airplane white noise is a key factor to why food and drink really do taste different in the air compared to on the ground.

So if you want to make your meal taste better, one option is to bring a bottle of Tabasco (less than 100ml of course). Another is to don a pair of noise-cancelling headphones.

Why are there still ashtrays on planes?

Our last niggle harks back to hazier days in the sky. By the start of the noughties, all planes were smoke-free and today every flight takes off to the "smoking is illegal on board" announcement. So why will you still find an ashtray on board? Because it's illegal not to have one, according to the Federal Aviation Administration (FAA).

The FAA list of "minimum equipment" for aircraft includes an ashtray in the plane toilet because if someone were to, illegally, light up a cigarette they still need to stub it out. Dropping it in the bin leads is a fire risk – back in 1973, almost everyone on board Varig Flight 820 from Rio de Janeiro to Paris died of smoke inhalation after a blaze that supposedly stemmed from a lit cigarette dropped into the lavatory trash. So according to the regulation: "Regardless of whether smoking is allowed in any other part of the airplane, lavatories must have self-contained, removable ashtrays located conspicuously on or near the entry side of each lavatory door."

According to flight attendants, the most common use of the ashtrays these days is by passenger mistaking them for door handles. Makes sense...

If you have air travel niggles, questions or myths that you would like us to challenge, tweet us at @IrishTimesMag and we’ll do our best to answer them