The physics of why this 1967 engine stops an airplane better than anything Boeing builds today are wild.The JT8D is a low-bypass turbofan. Almost all the air goes through the core. When those bucket doors deploy, they're redirecting nearly the entire exhaust flow. Pilots estimated 8,000 to 10,000 pounds of reverse force from a 15,000-pound thrust engine. That's a 55-65% reversal efficiency on a machine from 1967.Modern 737s run the CFM56, a high-bypass engine where most of the air flows through