We all know it’s been extremely hot over much of the Central U.S. this past week, and it’s going to be very hot in D.C. over the next few days. But did you know that this extreme combination of heat and humidity is taking a toll not only on us but the airline industry?
We’re able to fly because of the ingenious invention of the airfoil, or the specific shape of an airplane’s wing. As air moves over and below the wing, lower air pressure is created on top of it, therefore if lower air pressure is created then that means the air underneath the wing has higher pressure. Air will always flow from high pressure to low pressure, so that means the wing will want to rise or lift. When you’re taking off at an airport, there is a critical speed at which enough lift is created to carry you and the rest of your friends (not to mention all of your luggage too) into the air. So, the heavier the airplane the faster it needs to go to achieve liftoff. But lift also works better in denser air than air that’s not as dense; this is where weather becomes very important!
In the atmosphere, the hotter it gets the less dense the air becomes. Conversely, the colder the air gets the denser the air becomes. Also, the more humid the air is the lighter it is. This means in really hot temperatures air becomes less dense than it normally would. Add to this very high humidity levels, and you’ve really decreased the weight, or density of the air. Add to those relationships that air becomes even less dense the higher you go, and you’ve made some really big changes to the weight or density of the air!
So let’s say you’re set to go off into the wide blue yonder over the next few days, getting off the ground in your plane might be a little easier if you pack a little lighter! With all of this high heat and very high humidity, we’ve really decreased the density of the air. That means that your plane will have to go just a little faster in order to take off, which means you’ll need to travel farther on the runway too. In order to do those things, your pilot will have to keep the plane on full throttle a little longer which means the airplane will burn through a little more fuel a little faster than it normally would. So for a large airline that operates a lot of aircraft in extreme heat and high humidity days, you’re going to use a lot more gas when all of those planes are added up, which means you’re going to have to spend more money.
So if you’ve got a trip planned over the next week it might help if you and the rest of your passengers pack just a little bit lighter so that your plane weighs just a little bit lighter, which means it won’t have to go as fast to get you into the air.