In this photograph taken Feb. 8, 2016, a Southwest Airlines plane, front, waits to take off from a runway as a Frontier Airlines plane lands at Denver International Airport.
In this photograph taken Feb. 8, 2016, a Southwest Airlines plane, front, waits to take off from a runway as a Frontier Airlines plane lands at Denver International Airport. David Zalubowski AP
In this photograph taken Feb. 8, 2016, a Southwest Airlines plane, front, waits to take off from a runway as a Frontier Airlines plane lands at Denver International Airport. David Zalubowski AP