How they achieved the speed   Interesting mystery about SP Hundreds of pages written about it how they made it lighter shorter more powerful etc But nowhere they say what they did to increase the speed It flew just  kph slower than the speed of sound And its a good thing But neither Boeing themselves nor any other manufacturer ever tried to repeat this feat Why With modern airliners being able to cover up to  km why nobody makes them faster What was done to the airfoil in that regard Does anyone know a source where this angle is covered