Allegiant Air is expanding to three new cities as part of a 21-route expansion aimed at pandemic vacationers. The Las Vegas-based budget airline plans to start nonstop service from Portland, Oregon, in April and Key West, Florida, and Jackson Hole, Wyoming, in June. The airline offers rock-bottom ticket prices and charges extra for everything including carry-on bags, soft drinks and water, said one-way introductory fares range from $49 to $59 for the Portland, Jackson Hole and Key West flights. Allegiant doesn’t offer daily service on its routes, offering flights several times a week.