TAMPA — The numbers are grim. At eight hours, a healthy human being alone at sea enters a period of compromise. The U.S. Coast Guard's next measure of survivability: 13 hours, the time it takes for hypothermia to set in.
On Tuesday night, nearly 48 hours after officials believe the single-engine plane carrying a Tampa man and his friend crashed into the Gulf of Mexico, rescue crews suspended the search for them.
The families of Darien Peckham and Zachary Schlitt — one a medical researcher and breast cancer activist, the other a successful real estate developer — continued to hope for a miracle, even as Peckham's family planned a memorial for Thursday in Tampa.
''The Coast Guard sends its heartfelt sympathy to the families involved in this case," Lt. Cmdr. Tim Haws, Coast Guard Sector St. Petersburg's Chief of Response, said in a prepared statement. "After exhaustive search efforts we were unable to locate the missing pilots and the difficult decision was made to suspend our active search."
Peckham, 34, and Schlitt, 28, were both certified pilots, but neither the Federal Aviation Administration nor the Coast Guard has determined who was flying when an airport traffic controller in Jacksonville reported losing radar contact with them at 6:45 p.m. Sunday.
Family members said the two were returning from a trip to watch football in Tallahassee. They were headed to Vandenberg Airport in Hillsborough County when they disappeared 20 miles southwest of Yankeetown.
Rescue crews concentrated their search in two areas where debris — a seat and a bag with aviation headphones — were found Monday. The full search area extended from Cedar Key to the north and Largo to the south and covered 2,800 square miles.
The water in those areas ranges from about a few feet to 35 feet in depth, and temperatures are about 70 degrees, said Coast Guard spokesman Robert Simpson.
The two men were in excellent health, family members said.
The Citrus County Sheriff's Office also used sonar to try locate them and the plane, owned by Eagle Squadron, Inc., a Hillsborough County flying club.
On Tuesday, family members maintained a vigil at the Coast Guard station in Yankeetown.
Among them were Schlitt's father, Ron, a commercial pilot who also is a former lieutenant colonel in the Marine Corps and flew A4 Skyhawks.
At the Schlitt home in St. George Island in Franklin County, calls of support came in from friends and pilots around the world.
Pandora Schlitt's memories with her son included "lots of hunting and fishing together, lots of laughter, no regrets."
In Tampa Bay, Peckham's family members and longtime girlfriend, Karen Hohman, also waited hopefully for word of his rescue.
"He is an extremely capable pilot and has always been extremely cautious." Hohman said in a prepared statement. "My only concern and hope is that we find him. He is more loved than he could ever know."