Alaska Airlines and Hawaiian Airlines received approval from the U.S. Department of Transportation to proceed with their $1.9 billion merger. The airlines must maintain the value of their loyalty programs by allowing mileage transfers on an equal basis and ensuring key routes. The DOT has also required Hawaiian Airlines to adopt Alaska’s practices, such as guaranteeing family seating at no extra charge and compensating passengers for significant delays or cancellations. Hawaiian’s stock climbed 4% following the news.