* Airlines fly fewer flights, fuller planes
* US airlines flew 631 mln passengers domestically in 2009
* Fleet changes small with few orders in the pipeline
WASHINGTON, March 9 (Reuters) - Ongoing efforts by airlines to cut seats and flights will again ease pressure on the U.S. air traffic system in 2010, officials said on Tuesday.
The Federal Aviation Administration (FAA), which oversees the nation's air traffic network, forecast a 2.2 percent annual decline in takeoffs and landings by mainline, or major, and regional airlines this year. The projection follows a 6.9 percent drop in 2009.
Airlines continue to slash the number of available seats and are flying fuller and larger planes to control costs and improve pricing power on fares.
Mainline and regional airlines flew 631 million passengers on domestic flights in 2009.
The number of passengers expected to fly on those routes this year is expected to increase 0.4 percent, the FAA said. Regional airlines will account for the growth, while major carriers are expected to board nearly 1 percent fewer passengers domestically.
The total number of passengers for international travel on U.S. and overseas airlines is projected to grow 3.3 percent this year from 147 million in 2009, a lone bright spot for the industry. U.S. carriers handled about half the total last year.
Asia-Pacific is the fastest-growing region, the FAA said.
The mainline fleet of 3,666 planes is expected to shrink by 17 planes, or 0.5 percent, in 2010, with most of the decline due to the grounding of less fuel efficient models.
There are few new orders and most are going to replace planes, not expand operations, the FAA said. (Reporting by John Crawley; Editing by Richard Chang)