What is the maximum altitude referenced for "High" contacts?

The maximum altitude for what is considered "High" contacts is indeed 40,000 feet MSL (Mean Sea Level). This classification is important for various operational and navigational purposes, particularly in military and aviation contexts where altitude categorization can affect communication, radar tracking, and airspace management.

When dealing with radar and air traffic control, contacts above this threshold may require different protocols and procedures, emphasizing the significance of accurate altitude definitions. Identifying contacts as "High" helps ensure appropriate resources are allocated, and that air traffic controllers and pilots can maintain safe operational distances from other aircraft. Understanding these classifications can enhance situational awareness and operational effectiveness in airspace management.