LUDINGTON, Mich. - Authorities abandoned hope Saturday of finding alive four people missing since a small plane plunged into Lake Michigan while flying a cancer patient to the Mayo Clinic.

The pilot, 66-year-old Jerry Freed of Alma, Mich., was rescued following the crash Friday morning several miles off the west Michigan coast. After combing the area for 27 hours, rescuers concluded there was little chance anyone else had survived, said Petty Officer Brandon Blackwell of the U.S. Coast Guard's district headquarters in Cleveland.

"We can resume a search if credible information is received that persons missing may be alive," Blackwell told The Associated Press. "At this point, we saturated an area that's approximately 1,000 square miles ... and we've turned up nothing."

Also aboard the plane were co-pilot Earl Davidson, Alma school superintendent Don Pavlik, his wife Irene, and Dr. James Hall. All were residents of Alma, a central Michigan town 150 miles northwest of Detroit.

Don Pavlik was diagnosed earlier this year with cancer of the esophagus, said Tony Costanzo, the school board's vice president. Freed and Davidson had offered to fly Pavlik to the medical center in Rochester, Minn., for treatment, he said. Hall went along to help his ailing friend, Costanzo said.

Hall's wife told the Mount Pleasant Morning Sun that the doctor's medical bag had been recovered and that it contained a letter he apparently wrote in the final minutes before the plane went down.

Ann Hall said Saturday that the letter explained the plane lost power over Lake Michigan and that they turned back with the hope of reaching land.

"We are praying to God that all (will) be taken care of," James Hall wrote. "We love you. Jim."

Freed was released from the Memorial Medical Center in Ludington Saturday afternoon, hospital spokesman Bill Kerans said. He said Freed was denying interview requests.

The Mason County Sheriff Office said the effort to recover bodies and find the plane would be halted at sundown Saturday and resume this morning.

The plane took off from Alma about 9 a.m. Friday. Less than an hour later, Freed reported mechanical problems to the air traffic control tower in Minneapolis, said the Federal Aviation Administration, which was investigating the crash.

Battling a strong headwind over the lake, Freed decided to return to Michigan, the emergency management office said in a statement. It said the passengers were prepared for an emergency landing.

Freed's wife, Carol, told the Ludington Daily News her husband had checked the plane Thursday in preparation for the trip and had no concerns. She told the AP that Jerry Freed had flown many people to the Mayo Clinic over the years.

The lake's surface temperature was an estimated 68 degrees Friday and waves were 2 to 4 feet, authorities said.

Mason County Undersheriff Tom Trenner said Saturday that prospects weren't good for surviving more than a day in such chilly water.

State police dive teams were using sonar devices to find the sunken plane.

The U.S. and Canadian Coast Guards provided helicopters and fixed-wing planes for the search. Coast Guard boats were joined by vessels from the Mason and Oceana County sheriff's departments and Michigan Department of Natural Resources and Environment, along with number of volunteer boaters.

The search had gone on throughout Friday night. A bright moon and powerful searchlights gave crews a good view of the water's surface, said Coast Guard Petty Officer Chris Legard, who was aboard a 25-foot craft based in Ludington.

The water was choppy early in the evening but grew calm later, Legard said.

If any survivors "were close to us, we would have been able to see them," he said.