Frontier and Spirit Airlines are joining forces to become America’s fifth-largest airline. The airlines announced the $6.6 billion merger Monday, but haven’t revealed which banner the new airline will fly under. As reported by CNN, the merged airline will fall behind American, Delta, United, and Southwest for the most number of miles traveled by customers. In a statement, Spirit CEO Ted Christie said, “This transaction is centered around creating an aggressive ultra-low fare competitor to serve our guests even better, expand career opportunities for our team members and increase competitive pressure, resulting in more consumer-friendly fares for the flying public.”