Professionally, Mr. Hill was a metallurgist at the Johns Hopkins University Applied Physics Laboratory who eventually convinced his supervisors that he should be allowed to indulge his hobby at work. He became a pioneer in developing unmanned aerial vehicles — drones — for the military.
He was retired, legally blind as a result of macular degeneration and mostly deaf in the 1990s when he announced at a meeting of the D.C. Radio Control Club that he intended to fly a model airplane across the Atlantic — from the Canadian province of Newfoundland to Ireland.
With the exception of Mr. Hill, no one thought it was possible. According to international rules, a plane must weigh less than 11 pounds — including fuel — to qualify as a model. No such plane had flown even one-third as far as Mr. Hill was proposing.
Nevertheless, a group of other retired engineers and computer programmers soon joined the mission, swayed by Mr. Hill’s optimism and track record.
Working in his basement shop with the aid of special glasses and glue dyed red for better visibility, Mr. Hill perfected a tiny four-stroke engine that ran on camp-stove fuel, sipping just two ounces per hour. He mounted it on a balsa and Mylar skeleton with a six-foot wingspan. He did this over and over, building 29 versions of his design — the first 24 of which failed, crashed or disappeared in flight.
Meanwhile, Mr. Hill’s team helped raise tens of thousands of dollars. It perfected a computerized autopilot system to guide the aircraft on its long journey. And crew members flew Mr. Hill’s prototypes on countless test flights at a Montgomery County horse farm owned by Beecher Butts, an octogenarian aviation enthusiast.
In 2002, after four years of full-time work, the team traveled to Cape Spear, Newfoundland, for a first transatlantic attempt.
It was a disaster. Three planes went in the drink, two of them after traveling less than 30 miles. The computer experts on the team discovered a fundamental flaw in the navigational software.
Mr. Hill, undaunted, urged everyone — including his wife, who had driven a rental van for six days to deliver her husband and four airplanes to the launch site — not to give up.
After 12 more months of tinkering, the team returned to Canada. Mr. Hill threw his 25th plane, javelin-like, toward the east.
A tiny computer in the plane’s innards relayed information about its location and altitude. It behaved oddly, dipping and rising in an unpredictable fashion and at one point failing to communicate its position for three hours.