What is the maximum allowable altitude for VFR flight without an altimeter adjustment?

The maximum allowable altitude for Visual Flight Rules (VFR) flight without an altimeter adjustment is 18,000 feet Mean Sea Level (MSL). At altitudes below this threshold, pilots are not required to adjust their altimeters to the standard pressure setting of 29.92 inches of mercury. This regulation is in place to simplify operations for VFR pilots who may not have as much experience with altitude management as instrument flight rules (IFR) pilots.

Above 18,000 feet MSL, pilots must adhere to standard pressure settings for altitude control and visibility requirements become more stringent due to increased air traffic and the complexities of high-altitude flying. In practice, this means pilots operating below 18,000 feet can fly using local altimeter settings, allowing for easier navigation and vertical separation of aircraft operating in the airspace.