The main characteristic of a swept wing is that it reduces the total area of curvature of an aircraft, as compared to its straight-wing value, and it increases the critical Mach. Swept wing jets are designed to operate efficiently at transonic and supersonic speeds because of their high critical Mach. A swept wing jet incurs the risk of a nosedive as it approaches its critical Mach.
As a swept wing aircraft attains high speeds close to its critical Mach, aerodynamic buffeting occurs to divert some of the airflow from the wing and delay critical Mach. However, this creates a shock reaction that might cause Mach tuck and lead to a nose dive. Mach tuck and low-speed buffeting may also occur at low altitudes as the swept wings approach their stalling position, resulting in a nose dive.
The dangers of the coffin corner exist all the time, and swept wing pilots are advised to correct even the slightest signs of an impeding stall. At low altitudes, the typical recovery option involves application of full power to all engines, while at high altitudes, the jet's nose might be lowered below the horizon for full recovery. Critical Mach is the point at which the speed of airflow around the aircraft wings reaches the speed of sound before the aircraft.