Southwest Airlines is ending flights to four major airports — three of which are currently served by nonstop routes from Denver International Airport — and cutting back on flights to two others, the airline announced Thursday. Starting Aug. 4, Southwest will no longer fly in or out of Bellingham International Airport in Washington state, Cozumel International Airport in Mexico, Houston’s George Bush Intercontinental Airport and Syracuse Hancock International Airport in New York state, according to a Thursday news release from Southwest Airlines. The airline will also reduce operations at Hartsfield-Jackson Atlanta International Airport in Georgia and Chicago O’Hare International Airport, the release stated. Of the canceled flights, Southwest offered nonstop routes out of Denver to Bellingham, Cozumel and Houston’s George Bush.