That 4 hours is based on living near a major airport or flying into one and booking far enough in the future to get the best routes. If you live near one of the endpoint cities (say Austin TX out in the burbs), and you want to fly to another endpoint city (say SantaFe NM) and your choice of airline is poor (say united in this case) and you want to fly in two weeks. The flight/transfer time itself can be just as long as driving. It takes ~11 hours to drive that route, and the shortest listed flight on United for the date search I just ran is 8 hours 57 mins, up to 13 hours and 58 mins (out of the 4 united results returned on the first page). Add in security/etc and its likely even the 9 hour will take longer than the 11 hours driving.