The parent of United Airlines, the world\'s biggest airline, reported Thursday a steep fall in second-quarter profit on weak revenue growth. United Continental Holdings, Inc. said it had net income of $339 million in the April-June period, compared with $538 million in the year-ago period. Earnings of $1.41 per share, excluding special items, fell far short of the $1.70 expected by analysts. The company, known by its ticker symbol UAL, said revenues edged up 1.3 percent, to $9.9 billion, missing estimates of $10.0 billion. The biggest airline by traffic also was hit by higher fuel prices, a major driver of a 4.0 percent increase in operating costs. Passenger revenue increased 2.3 percent to $8.8 billion, while cargo revenue tumbled 16.1 percent to $265 million. UAL has been struggling with the integration of United and Continental airlines since their 2010 merger. In November 2011, it received US Federal Aviation Administration approval for a single operating certificate for United and Continental after an 18-month process of aligning the two airlines\' operating policies and procedures. The company booked $206 million in special charges. \"I want to thank my co-workers for all they did to help us earn a profit this quarter,\" Jeff Smisek, UAL president and chief executive, said in a statement. \"While we still have work to do, we are making the right investments in our future, and we look forward to delivering the benefits of those investments to our customers around the globe.\" United Airlines and United Express, a flight connection carrier, operate an average of 5,574 flights a day to 377 airports on six continents. United carried 142 million passengers in 2011, more than other carrier.