NEW YORK — Drivers have long known that slowing down on the highway means getting more miles to the gallon. Now airlines are trying it, too – adding a few minutes to flights to save millions on fuel. Southwest Airlines started flying slower about two months ago, and projects it will save $42 million in fuel this year by extending each flight by one to three minutes. On one Northwest Airlines flight from Paris to Minneapolis earlier this week alone, flying slower saved 162 gallons of fuel, saving the airline $535. It added eight minutes to the flight, extending it to eight hours, 58 minutes. That meant flying at an average speed of 532 mph, down from the usual 542 mph. ‘It’s not a dramatic change,’ said Dave Fuller, director of flight operations at JetBlue, which began flying slower two years ago. But the savings add up. JetBlue adds an average of just under two minutes to each flight, and saves about $13.6 million a year in jet fuel. Adding just four minutes to its flights to and from Hawaii saves Northwest Airlines $600,000 a year on those flights alone. United Airlines has invested […]