What is the maximum allowable altitude for VFR flight in controlled airspace?

For VFR (Visual Flight Rules) flight in controlled airspace, the maximum allowable altitude is 18,000 feet MSL (Mean Sea Level). This altitude marks the boundary between the lower altitudes where VFR operations occur and the transition to the en-route structure for IFR (Instrument Flight Rules) operations, which begins at 18,000 feet.

Flying at or below this altitude allows pilots to navigate visually while still adhering to the rules that govern operations in controlled airspace. Above this altitude, the airspace is primarily managed by IFR, and pilots are typically required to file flight plans and operate under IFR regulations. Therefore, VFR operations are specifically limited to ensure safe separation from IFR traffic, which generally dominates the higher altitude airspace.

The other altitude options pertain to various airspace classifications and may reflect different operational limits or requirements, but in the context of VFR in controlled airspace, 18,000 feet MSL is the established maximum.