The Downside of an Airplane’s Descent

Pre-pandemic, in 2019, airlines’ greenhouse gas emissions were at a recent high. More passengers and more flights created more fuel-related emissions. Then, as you might expect, we had a (temporary?) pandemic dip:

Typically, the attempt to become more green has focused on biofuels. Instead, though, all you have to do is go down differently.

Greener Airlines

You know what it’s like to move from 42,000 feet to the runway. Occupying more than 30 minutes, the downward journey is rather like descending a staircase. Called the Step Down Approach, it wastes fuel and increases emissions because pilots have to power up their engines each time they level off:

Aware of the downside, the FAA (Federal Aviation Administration) has begun to approve a continuous descent (Optimized Profile Descent) in which a plane’s engines are almost idling. At the airports that implement OPD, they project annually cutting fuel use by two million gallons and emissions by 40 million pounds.

Our Bottom Line: Negative Externalities

As economists, we can say that community devastation from a weather disaster is one of many examples of the impact of the global warming that excessive emissions create. Because unrelated third parties–people having nothing to do with airlines– experience the impact, it is called a negative externality. To minimize the negative externalities they help to cause, airlines can design more efficient routes, build better aircraft, and buy larger planes that seat more passengers.

We should note that, at 2.5 percent, aviation related emissions are a small proportion of the total:

However, their negative externalities are typical.

My sources and more: My go-to for airline info has always been “The Middle Seat” column from Scott McCartney. This time, I had to go back to 2019 when he looked at how green the airlines were. (Sadly, Mr. McCartney said his December article was his last.) From there, my up-to-date statistics and analysis came from the FAA,  Our World in Data, the BLS. and the BBC. Finally, I do want to thank the Axios morning news podcast for alerting me to the descent’s downside.