The Justice Department and officials in six states have filed a lawsuit to block a partnership formed by American Airlines and JetBlue, claiming that it will reduce competition and lead to higher fares. The Justice Department said Tuesday that the agreement will eliminate important competition in New York and Boston and reduce JetBlue’s incentive to compete against American in other parts of the country. Attorney General Merrick Garland said the lawsuit was about ensuring fair competition that lets Americans fly at affordable prices. “In an industry where just four airlines control more than 80 percent of domestic air travel, American Airlines’ ‘alliance’ with JetBlue is, in fact, an unprecedented maneuver to further consolidate the industry,” Garland said in a statement. “It would result in higher fares, fewer choices, and lower quality service if allowed to continue.” American and JetBlue vowed to fight the lawsuit and to continue their alliance unless …