A new direct flight service has opened at Louisville International Airport.United Airlines will now provide nonstop flights to and from Denver, Colorado. Airport Authority Board of Directors Chairman Philip Lynch says there's a demand for direct flights to Denver, and this isn't the first time they've been offered."Frontier Airlines that was in here before it went into bankruptcy offered direct service and actually did really well, but then when Frontier went into bankruptcy, they pulled back everything, even though our service was making money for them but the whole airline wasn't," he says.Frontier went bankrupt in August 2008. 50-seat planes are currently making the direct flights to Denver, but United plans to upgrade the planes to 66 seats in April."The airplane itself is a Sky West regional airplane—it's a 50-seat aircraft. In April, we'll upgrade that airplane to a 66-seat aircraft with a first class on it," says Michael Beirne with United.Denver is the 25th city to have a nonstop service from Louisville.