What do you need to do when climbing above 18,000 feet into Class A airspace?

When climbing above 18,000 feet into Class A airspace, it is essential to set the altimeter to 29.92 inches of mercury. This practice aligns with the standard pressure setting used throughout the United States' Class A airspace. Class A airspace is defined from 18,000 feet up to and including flight level 600, where a consistent altimeter setting is critical for maintaining vertical separation between aircraft.

Setting the altimeter to 29.92 ensures that all pilots are referencing the same altitude above sea level, which is vital for safe navigation and collision avoidance in a crowded airspace environment. This standardization helps in maintaining an organized and predictable traffic flow as all aircraft will use the same reference point for altitude reporting.

Although communication with ATC for clearance, changing the transponder code, and confirming weather conditions are also important aspects of flying, they pertain to other regulations and procedures. The primary requirement when entering Class A airspace is the adjustment of the altimeter to the standard setting.