Video taken from a Coast Guard patrol boat in the vicinity of the suspension bridge shows the aircraft approaching the bridge at a low altitude and flying under the main roadway at 2:50 pm on Sunday, June 28.
Nearly two months later, investigators are asking the public to help find the renegade pilot.
Authorities say the bridge, which carries Interstate 75, was packed with hundreds of cars at the time, traveling in advance of the July 4 holiday weekend. "This was extremely reckless behavior on the part of the pilot, and it imperiled the safety of everyone on the bridge that day," Sgt. Gary Demers of the state police said in a statement. "We hope that someone can come forward with information to help us make sure it doesn't happen again."
Federal Aviation Administration regulations do not specifically prohibit flying under a bridge — common sense does — but do bar pilots from flying within 500 feet of "any person, vessel, vehicle, or structure" when over open water or sparely populated areas. (Otherwise, they must maintain an altitude of 500 feet.)
The sole driveable link between the lower and upper peninsulas of Michigan, the roadway of the Mackinac Bridge stands just 199 feet above the water at its highest point, according to the Mackinac Bridge Authority, meaning the closest to the span a pilot of a fixed-wing aircraft can legally fly is 699 feet above ground level.
The FAA's enforcement division can charge between $1,100 and $27,500 for a violation of its rules, depending on the circumstances.