United Continental Holdings Inc. said expenses are rising more quickly than usual because of new employee contracts that have brought the airline to the brink of labor peace after years of acrimony. Costs for each seat flown a mile are expected to climb 4.75 percent to 5.75 percent in the current fourth quarter, excluding fuel and certain other items, the Chicago-based carrier said in a statement Monday. The increase, which the carrier said was driven by recently ratified labor deals, compares with no change in last year’s fourth quarter and a gain of 1.2 percent in 2014. The higher costs may slow efforts to boost profit margins to the level enjoyed by rivals such as Delta Air Lines Inc., United Chief Financial Officer Andrew Levy said on a conference call with reporters. Closing the gap with Delta and American Airlines Group Inc. has been a key goal of Levy’s boss, Chief Executive Officer Oscar Munoz, who is expected to outline his plan to boost profits on Nov. 15. “Investors may again question UAL’s ability to close the margin gap to peers,” Andrew Didora, an analyst at Bank of America Corp., said in a note to clients, referring to United’s ticker. He cited a “disappointing cost outlook.” United was little changed at $53.03 at 6:40 p.m. in late trading in New York. Labor ‘Reset’ “We’re going to pull all the levers we can” to offset the higher employee costs, Levy told reporters Monday, calling the contract agreements a “reset” of labor relations. After years of battling labor unions, United has all of its major employee groups under contract or nearing a contract vote for the first time since its 2010 merger with Continental. In the third quarter, adjusted earnings of $3.11 a share topped the $3.06 average of analysts’ estimates compiled by Bloomberg. Revenue fell to $9.91 billion, the airline said in a separate statement Monday. That was in line with the average analyst estimate. Passenger revenue for each seat flown a mile, or unit revenue, may decline 4 percent to 6 percent in the current quarter, the airline said. The capacity of flights and seats is projected to climb 1 percent to 2 percent in the last three months of the year. United shares have gained 40 percent since hitting their low on June 27, as investors gambled that the company is on the verge of a turnaround. Munoz has a new management team that includes President Scott Kirby, who joined United from American. Investors may get their first chance to hear from Kirby on a United conference call on Tuesday at 10:30 a.m. New York time.