"Because aircraft engines don’t throttle up and down during a continuous descent arrival, there are also significant reductions in noise and emissions. Keeping engines at idle power can cut emissions of nitrogen oxides by nearly a third, and reduce noise by 6 decibels along certain portions of the flight path - both significant reductions that would improve the environment in the vicinity of airports. And the technique could cut two minutes off the approach and landing portion of a flight. While that doesn’t seem like much, it could result in more efficient utilization of aircraft and reductions in flight times for crews"
PhysOrg.com on the innovation being tried at Atlanta's Hartsfield airport