Fastening the seat belt buckle and knowing your flight is on its way to its destination: Nice. Getting stuck in a tarmac traffic jam and waiting for your flight to take off: Not so nice. Turns out the wait is also not nice for the planet.
Flying in an airplane is already one of the most emissions-intensive things you can do. Globally, aviation produced over 1 billion tons of carbon emissions in 2019, more than 2 percent of all human-generated emissions—more than either shipping or rail. Aircraft engines also emit nitrogen oxides, soot particles, and water vapor, which also contribute to warming the planet.

That’s because airplane engines are designed to operate in the air, says Hamsa Balakrishnan, a professor of aeronautics and astronautics at MIT who studies airport operations. When aircraft are waiting at their gates, they rely on auxiliary power systems to keep just the essentials running. But once a plane pushes back, it starts running its engines, and burning fuel. Idling at airports also hurts local air quality, says Balakrishnan—people live and work closer to airports than they do to the middle of the sky. It’s noisy, too.
Now the Federal Aviation Administration and NASA have created a system to smooth the takeoffs and landings, wringing out delays and unnecessary emissions in the process. Real rocket scientists were involved—the system grew out of NASA’s work to help spaceships establish steady trajectories into space.