On April 28th, 1959, Air Force Captain John S. Lappo, a native of Muskegon, Michigan, flew his B-47 nuclear bomber under the Mackinac bridge connecting southern Michigan to the so-called “Upper Peninsula”.
The Mackinac Bridge is five miles long but there is only 155 feet maximum clearance between the bottom of the deck and the waters of the Great Lakes (Lake Huron and Lake Michigan) below. The B-47 bomber is 28 feet high, meaning there wasn’t much margin for error in Lappo’s flying.
The B-47 was one of America’s first jet-powered bombers. The B-47 first flew in 1947 and was the Air Force’s primary medium range nuclear bomber until 1965. The B-47 could cruise at 550 miles an hour and carry 25,000 pounds of bombs. In a nuclear war it would carry two Mk. 15 thermonuclear bombs, each of which had an explosive yield of 3.8 megatons. More than 2,000 of the bombers were produced.
By today’s standards, the B-47 was incredibly unsafe—203 aircraft were lost to crashes (10 percent of the airplanes produced) killing 464 aircrew.
As Task & Purpose points out, U.S. Military aircraft at the time were prohibited from flying with 500 feet of the ground. According to newspaper accounts at the time the entire incident went unreported and indeed nobody on the ground may have actually seen it. Tragically, there is no video evidence of this incredible (and dangerous) stunt.
Nevertheless Lappo was reported through the military chain of command and brought before a court martial. Lappo was fined $300 (the equivalent of $2,615 in today’s dollars) to be paid $50 a month over a six month period.
Lappo was also grounded—forever. That having been said, he did retire after two more promotions to the rank of lieutenant colonel, so he wasn’t in the doghouse forever.
Source : Kyle Mizokami, “Sixty Years Ago, a Pilot Flew a B-47 Nuclear Bomber Under Michigan’s Mackinac Bridge“, Popular Mechanics, April 30, 2019.