PRNewswire -- Delta Air Lines today announced that it has installed Wi-Fi on nearly half of its domestic mainline fleet, making the airline the world's leading provider of in-flight connectivity. Of the more than 300 airplanes Delta operates on U.S. routes, 139 are equipped with Gogo(R) Inflight Internet, including the entire MD-88 fleet. In addition, the MD-90 fleet will be complete by the end of May with the remainder of the domestic fleet scheduled for completion by September. Delta offers more Wi-Fi onboard than any airline worldwide.