What is the standard Vertical Separation Minimum (VSM) for aircraft flying in the same direction above FL290?

The standard Vertical Separation Minimum (VSM) for aircraft flying in the same direction above Flight Level 290 (FL290) is indeed 4000 feet. This requirement is established to ensure adequate separation between aircraft, particularly given the increased speed and altitude at which they operate.

At higher altitudes, the potential for wake turbulence and other factors such as vertical speed can become more pronounced, necessitating a greater vertical separation to maintain safety. The 4000 feet allows for a buffer that accommodates variations in altitude due to air traffic control instructions, atmospheric conditions, and other operational factors. In contrast, altitudes below FL290 have different separation minima due to the generally reduced risk factors and operational considerations present at lower flight levels.

Understanding these separation minima is crucial for pilots and controllers to ensure safe operations in busy airspaces, particularly as traffic increases at higher altitudes.