Didn’t happen before or since.
In 1991 a Lauda Air 767 tore itself apart in midair when the thrust reverse on the number 1 engine deployed on it's own. That hadn't happened before. That hasn't happened since.
“Didn’t happen before or since.”
Not exactly.
Center-line fuel tanks have a history of explosions. There is a history of aircraft loss due to wire chaffing, electrical arching and such. While the short-list of examples provided below are 707-type, it is a threat that all jets have because electrical wires and hydraulic lines are routed through fuel tanks for cooling. 707, fighter aircraft, 747, it is almost universal that all jets are designed that way.
KC-135: History of Destroyed Aircraft (USAF version of the B-707 is the KC-135: https://airrefuelingarchive.wordpress.com/2009/06/04/kc-135-history-of-destroyed-aircraft/
“22-Jun-59 57-1446 A Walker AFB Main fuel tank explosion on ramp (maintenance)”
“3-Jun-71 58-0039 Q Torrejon AFB Crashed following in-flight explosion of the nr. 1 main fuel tank. Chafing of boost pump wires in conduits was determined to be as a possible ignition source.”
“13-FEB-87 60-0330 A Altus AFB Landed on the runway at altus afb on fire, cause was an arc in the fuel vapor area due to a compromised coax from the HF radio, aircraft subsequently burned to the ground in the infield after it rolled off the runway”
“4-Oct-89 56-3592 A Loring AFB In-flight explosion (aft body tank) during approach”
FAA: “ Since 1959 there have been 18 fuel tank explosions on transport category airplanes” http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%20120-98A.pdf
The cost of complying with regulations that remove the center line tank explosion threat is tens upon tens of millions of dollars, and the airlines absorbed that cost. . .and the airlines and OEM know the systems and if they knew the tank was not the cause then there would have been lawsuits and public hearings challenging the regulation. And with the threat of another center line tank explosion, the airlines and OEM have to fix the problem otherwise they would be sued out of existence. . .the fact the airlines and OEMs did not challenge the regulation and made the changes means they knew it was the cause.
Mitigation study: https://www.fire.tc.faa.gov/pdf/systems/AIAAFDC32143b.pdf