US Airways and American Airlines closed their $17.7-billion merger Monday, creating the world’s largest airline. So what does it mean for the average traveler? Not a whole lot so far and the airlines say it’s business as usual. But changes to the airlines’ operations will start next year, and will soon accelerate as US Airways and American work to combine their business. Charlotte Douglas International Airport will be the combined airline’s second-busiest hub, behind only Dallas/Fort Worth in the airline’s number of daily flights. The new carrier will be called American Airlines and will be headquartered in Fort Worth. US Airways and American will begin combining their frequent flyer plans as early as the first week in January. Flyers will be keep all of their miles, and will be able to combine their miles from both airlines. The airlines will operate separately for a year and a half to two years, according to a US Airways spokeswoman. US Airways is also leaving the Star Alliance in the first quarter next year and joining the American-led Oneworld alliance. The airlines are setting up websites to help travelers keep track of changes, but www.USAirways.com/arriving is active.