When Jets Downshift Overhead

A common sound in the skies over Princeton is a sudden drop in the pitch of commercial jets flying far overhead. It sounds like, and is, a relaxing of the engines, an easing back. An article from 1977 found on the web reports on what was at the time a new way for jets to smoothly descend while reducing fuel consumption and noise. My understanding from an in-law who flies the president of Argentina around, is that jets these days pretty much coast in from 50 miles out, which would correlate with Princeton's distance from airports in Newark and New York.