More than 80 percent of Alaska Airlines' customer reviews on TripAdvisor were rated as "very good" or "excellent," which shows why it's No. 1. "Alaska has a peerless frequent-flyer program and a high rate of customer satisfaction, with only 0.58 complaints lodged per 100,000 fliers — less than a third that of other airlines," Kelly said. "Its robust cabin features include one of the youngest fleets in the US and little features, like ensuring that each of its passengers has electric power at their seat."