OCEAN CITY, Md. (AP) _ Rescue crews searched a remote marsh on Maryland's Eastern Shore today, hoping to find one of two military pilots whose planes crashed within hours of each other. The search for the other pilot was called off.

An Air National Guard A-10 warplane plane went down about 1:25 p.m. Thursday, submerging in the marshes between Fishing Bay and the Wicomico River, said Maj. Laura Feldman, an Air Force spokeswoman.

``We had to use all-terrain vehicles to get the military people to the scene,'' said Wylie Abbott, assistant fire chief of the Elliott Fire Department. ``It's all marshy bog out there.''

Maj. Chris Cleaver, a spokesman for the Pennsylvania National Guard, said the search for the pilot, whose name has not been released, resumed at dawn today. He said it has not been determined yet whether the pilot ejected before the plane crashed or remains in the A-10's cockpit.

``We know the location of the aircraft, but it's in an extremely remote and inaccessible site,'' Cleaver said. The A-10 was flying from Willow Grove Air Reserve Base in Pennsylvania on a maintenance test flight when it went down.

The two crashes, which happened in clear weather, did not appear to be related.

The search for the second pilot, Patrick Gregoire of Portland, Ore., was abandoned Thursday night after the Coast Guard searched 1,100 square miles of the Atlantic Ocean near Ocean City, only to find the pilot's life vest, personal effects and a four-foot piece of wing.

``The signs of things we've found would indicate there's a good chance he didn't make it,'' said Coast Guard Petty Officer Harry Craft.

The single-seat Marine Corps F/A-18 Hornet crashed Thursday just after 9:30 a.m. about 40 miles east of Ocean City while on a training mission, the Coast Guard said.

The attack jet was based at Andrews Air Force Base in suburban Maryland as part of a Marine Corps Reserve unit, said Gunnery Sgt. Don Hooper, a Marine Corps spokesman. Gregoire was living in Springfield, Va. His age wasn't available.

Frank Crispin, a 49-year-old insurance agent Derry, Pa., was on a charter boat when he heard a ``boom'' and saw ``a big plume of water.''

``It looked like a cloud coming out of the water. I said, `I think a bomb went off over there,''' he said.

Thursday's crashes followed an announcement that about a quarter of the Air Force's planes would halt routine training flights and exercises today to go over safety. They also came in the wake of four military crashes in the last month, including the C-130 cargo plane that crashed Saturday in Wyoming, killing all nine aboard.