What is meant by the term "coffin corner" in aviation?

The term "coffin corner" in aviation refers specifically to the altitude where stall speed and minimum drag airspeed converge. At this altitude, the aircraft operates at a high risk of stalling when attempting to maintain level flight due to the proximity of stall speed to the airspeed needed for optimal performance.

When a pilot flies at an altitude that represents the coffin corner, they are operating at a point where any increase in load factor or a decrease in airspeed could lead to a stall. This situation is particularly significant in high-performance or jet aircraft, where both stall speed increases with altitude due to thinner air and drag can increase due to various factors. This phenomenon makes it critically important for pilots to manage their speed and altitude carefully to avoid entering a dangerous flight regime.

The other options presented do not accurately describe the concept of coffin corner. The convergence of stall speed and cruise speed is not the focus of the term, and it does not pertain to the lowest safe altitude for flight, nor does it relate to aircraft avionics location. Understanding coffin corner is essential for safe flight operations at high altitudes, especially when dealing with the performance characteristics of an aircraft.