An AP story in the San Francisco Chronicle for 23 August (page D7) starts:
"In a travel season rife with late arrivals and canceled flights, several airlines have begun flying at lower altitudes, trading fuel efficiency for on-time arrivals.
The FAA gave airlines approval more than a year ago to operate some short flights-- up to 500 miles-- at between 8,000 feet and 23,000 feet...."
The story says United sends 30-40 low-altitude flights out of O'Hare each day, "saving an average of two minutes on the ground and about 10 in the air, spokesman Joe Hopkins said." It also says AA will shortly start low flights (at Chicago?) and that NW flies them out of MSP and DTW. It also says what you'd expect: "But low flights are generally kept above 18,000 feet."
Can anyone begin to explain how flying at FL180 -FL230 will save ten minutes in the air? Can anyone give an example comparison?