The United States and Cuba signed a deal Tuesday restoring commercial air traffic for the first time in five decades, allowing dozens of new daily flights to bring hundreds of thousands more American travelers a year to the island as early as this fall.Immediately after the signing, the U.S. Department of Transportation opened bidding by American air carriers on as many as 110 U.S.-Cuba flights a day more than five times the current number.All flights operating between the two countries today are charters. Barring other major announcements, the restart of commercial flights will be the most significant development in U.S.-Cuba trade since Presidents Barack Obama and Raul Castro announced in late 2014 that they would begin normalizing ties after a half-century of Cold War opposition.