NEW YORK (CNN/Money) - United Airlines, the bankrupt carrier that hasn't turned a profit since the second quarter of 2000, flew back into the black with a profit in May, the world's No. 2 airline reported Tuesday.

In a filing with the Securities and Exchange Commission, United said it earned $64.3 million in the month on revenue of $1.1 billion. The airline reported a net loss of $374.9 million in April on revenue of $1.0 billion.

The airline won new labor agreements from its unions in April that took effect in early May. Those agreements are expected to save the carrier about $2.56 billion a year compared with the pre-bankruptcy labor pacts.

The company previously reported that miles flown by paying passengers in May had fallen 13.8 percent from a year earlier to 7.9 billion. But even deeper capacity cuts had allowed it to fill 77.2 percent of available seats, up from 73.2 percent a year earlier.