Is it Safe to Fly When it’s Really Hot Outside?

Can your plane take the heat?

Is it safe to fly when it’s really hot outside? With record or near-record temps becoming more common, there’s been a lot of media coverage about flights that are cancelled due to the extreme heat. Why do these flights get cancelled? Are the flights that don’t get cancelled less safe? These are both excellent questions.

Yes, it is absolutely safe to fly when a heatwave comes to an airport near you. Commercial airliners are designed and built to handle all kinds of elements: wind, rain, snow, and even severe heat. In fact, temperature is one of many variables that is always considered when it comes to aircraft performance and a plane’s ability to fly. One of the main reasons for this is because temperature can influence air density (how many air molecules are present in a given volume of space). This is relevant because as it gets warmer outside, the air expands, becoming less dense. So, why might this matter for your flight?

…temperature is one of many variables that is always considered when it comes to aircraft performance and a plane’s ability to fly.

The wings need air in order to produce lift. If the air gets really warm and expands, there will be less air molecules to flow under and around the wing. This “thinner” air, results in the wings producing less lift than normal. They will still produce lift, just not quite as much. So yes, the plane can and will still fly, but it consequently may need more speed to get a sufficient amount of air flowing under the wings, thereby enabling it to become airborne.

Well, if the plane has to go faster in order to takeoff, that means one of two things will need to happen. Either it will require more runway, allowing the plane to accelerate to takeoff speed, or it will need to shed weight. It’s no mistake then that most airports have at least one very long runway. For example, Phoenix’s Sky Harbor Airport, which is located in one of the warmest locations in the US, has one runway that is over 11,000 feet long. Additionally, as part of the pre-takeoff process, variables like the current temperature, the length of the runway, and a host of other factors are always computed before your flight will ever take the runway. These performance calculations predict airplane performance and will ensure that every flight can actually liftoff safely and with ample safety margins built in, in spite of higher than normal temperatures outside. Only in very extreme cases will the latter choice of reducing weight have to be exercised. However, in those instances, passengers and/or cargo may be removed to increase aircraft performance well above the required level.

So, if longer runways or reduced weights can potentially solve this problem, why are some flights still cancelled due to high temperatures? Well, the overwhelming majority of airliners are still able to fly even in extreme heat and thus will not be cancelled. Unfortunately, there are a small handful of regional jets that are adversely impacted to the point of being grounded when temperatures go above 118 degrees F (Boeing and Airbus jets can operate up to 126 degrees F). These smaller planes are designed to carry less people and cargo than most airliners. This means that even with access to longer runways they still don’t have the flexibility of further reducing their weight enough to offset the high temps and thin air. For all practical purposes, these planes would still be able to fly, but they wouldn’t be able to do so with the additional safety margins that are always required. In the rare cases where this occurs, the flight in question get scrapped. It’s unfortunate, but it’s done in the name of safety.

…there is little to no chance of high temperatures causing your flight to be cancelled.

Fortunately, there are very few places where it actually gets to be anywhere near 118 degrees (it’s also rare for it to happen in those locations). So, while temperatures do seem to be trending upwards and will always be a consideration, there is little to no chance of high temperatures causing your flight to be cancelled. Even more importantly, there is zero chance of extreme heat impacting the safety of your flight. This is because air temperature is one of the variables included in the performance calculations that the airline will complete (and that the pilot’s will verify) prior to each and every flight. Your flight will only be allowed to depart if it is able to takeoff and do so with an ample safety margin. So, even if you find yourself in extreme heat you don’t have to sweat whether or not your flight will be impacted by those high temperatures.