All three airlines reported losses in the second quarter compared with profits in the period a year ago.

They joined other big airlines, including American, Continental and Delta, in posting second-quarter losses in the past week. Northwest Airlines reports its results today.

Domestic airlines have been hit hard by record fuel prices, which are up 93.7 percent in North America compared with a year ago. The airlines have cut flights, grounded planes, raised prices and imposed fees for features that used to be free, like checking bags.

United, the second-biggest domestic carrier behind American, said Tuesday that it would cut its capacity by 11 percent in the fourth quarter, including a 16 percent cut in domestic flying, and a 7 percent reduction in international flights.

For the full year, United's capacity is expected to drop 7.5 to 8.5 percent compared with 2007.

The chief operating officer, John Tague, said United was seeing a ''developing overcapacity in the international marketplace.'' United recently announced that it was grounding some big Boeing 747 jets, and dropping several international routes.

The airline, based in Chicago, said it would also eliminate 7,000 jobs by the end of the year, as it reported a net loss of $2.73 billion, compared with a profit of $274 million in the second quarter a year ago.

JetBlue reported a net loss of $7 million, less than analysts expected. It earned $21 million a year ago.

US Airways said Tuesday it lost $567 million in the second quarter, including noncash charges, and also said it was cutting back again on its flights. It said it would cut flights by 4 percent this year, up 1 percent from its previous announcement, and by 6 percent in 2009, up 2 percent.