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My understanding is that a normal jet aircraft will have a real hard time approaching and breaking the speed of sound at whatever density, temperature it's at. This is because at the speed of sound, the cone shaped shock wave would intersect the relatively wide wings causing drag and mechanical shock.
Unfortunately not.
At Mach 1,0, the shock cone has apex angle of 180 degrees - it is a flat plane supported at the nose, and will not touch nose.
However, a big issue with sound barrier is backwards shift of the centre of lift. Concorde had to pump fuel backwards during acceleration to transonic. A subsonic airliner does not have such pumps. If it were to accelerate near the speed of sound, it would suffer a Mach tuck - as the centre of lift moves backwards, the plane drops nose and enters into dive, the elevator authority is not enough to raise nose, so the plane accelerates in a supersonic dive till it meets ground or is broken mid-air by excessive aerodynamic forces.