The wreckage of one plane and the body of its pilot, Jay Blum, 39, of Berwyn, Pa., were pulled from the waters just off Cape Henlopen State Park shortly after the accident Sunday.
The search for the other pilot was called off Sunday evening because of poor underwater visibility and rapid currents that made conditions difficult for divers. The search was to resume about 10:30 a.m. Monday.
Meanwhile, two small biplanes simulating a World War I dogfight collided at an air show in central Canada, killing both pilots instantly.
Searchers believe the plane is just off a breakwater in Delaware Bay water ranging from about 15 to 50 feet deep. Crews from the Delaware State Police and local fire companies will resume looking for the wreckage about 10:30 a.m., said state police spokesman Lt. Joseph Aviola.
"The pilot is possibly still with the plane," Aviola said.
Blum's plane, a Rutan Long EZ, is registered to ACE Aero LLC of Bryn Mawr, Pa., The other, a Vans RV8, is registered to Ralph D. Morgan of Rehoboth Beach, said Kathleen Bergen, a spokeswoman for the Federal Aviation Administration.
The FAA and the National Transportation Safety Board sent investigators to the crash site. The Coast Guard sent rescue boats from Indian River, Del., and Cape May, N.J., and a rescue helicopter from Atlantic City.
Authorities said six experimental planes from a group called The Vultures had just completed a maneuver called Six Ship Opposing and had broken off into separate groups of three when two planes in one group collided, sending both plunging into the bay.
A seventh plane, acting as a "spotter," was flying separately from the others, police said.
Dale Byers, 62, and his wife Nancy, 60, of Cape May, N.J., witnessed the collision while riding the ferry to Lewes with their grandson Matt Colagreco, 15.
"We thought, oh, we're going to get a free air show," said Byers, recalling how the mood aboard the ferry changed in an instant when the two planes collided.
"It just made me sick to my stomach," he said.