We love hearing from one5c readers, and we read every message—even if we don’t always have time to reply to them all. So we’re sharing our answers to questions that have takeaways everyone can use.
I read a few years back that if jets flew a couple thousand feet higher the environmental damage would be far less. Less drag, less fuel consumption, etc. But is this being done or pushed onto the airlines?
Flying higher in the atmosphere doesn’t necessarily cut an aircraft’s environmental impact. Yes, the air is thinner the higher you go, but drag isn’t as big of a factor at cruising altitude as it is in other segments of a flight. The biggest fuel drains happen at takeoff and landing, so climbing higher stands to embiggen those impacts. Also relevant to fuel drain: Commercial aircraft engines need oxygen to work, so when the air is thinner (that is, less oxygen dense) they need to work harder.
That’s just the carbon dioxide piece of the puzzle. Contrails—the long clouds that form behind jets when water vapor in their exhaust mixes with cold air—are more likely to form at higher altitudes than lower ones. Some of these trails can hang out in the atmosphere and create a warming effect. One estimate from the U.N. Intergovernmental Panel on Climate Change says that contrails account for 35% of aviation’s total global warming potential. One 2020 analysis did find that a flying a couple thousand feet higher can reduce contrails, but the benefits are likely canceled out by other factors.
There are, for instance, other gases in a plane’s emissions soup to consider. Nitrogen oxides from plane exhaust can create a dangerous mix in the sky. Way up in the air, those gases react with the atmosphere to create ozone, a powerful greenhouse gas. They also mix with other exhaust, including water vapor. Yup, that means potentially more potent contrails.
So, yeah, a couple thousand more feet could conceivably hurt more than it helps. Besides, the aviation industry should be focusing its efforts elsewhere if it’s serious about decarbonizing.
What do we mean? Picking up the pace in its adoption of sustainable aviation fuel (SAF), which is derived from sources like ethanol or agricultural waste rather than fossil fuels. Despite lofty promises, carriers’ SAF use amounts to mere drops of their fuel consumption while their overall emissions continue to rise, according to a Bloomberg Green analysis. At British Airways, for instance, SAF accounted for 1.9% of fuel consumption, but emissions from burning fuel jumped by 5%. That trajectory is on par with the whole of the industry.