What altitude must be maintained when flying under VFR in controlled airspace?

When flying under Visual Flight Rules (VFR) in controlled airspace, the requirement is to maintain an altitude of at least 2,500 feet Above Ground Level (AGL). This regulation is in place to ensure that aircraft are sufficiently separated from both the terrain and other aircraft operating in the vicinity, particularly in more congested airspaces like Class B, C, and D airspace.

Maintaining an altitude of 2,500 feet AGL provides a buffer that enhances safety by reducing the risk of collisions and allowing for greater visibility in relation to surrounding obstacles and traffic. This altitude requirement is particularly important as it helps pilots avoid low-level airspace congestion and provides a safer margin for maneuvering when encountering unexpected situations.

In the context of the other options, maintaining altitudes below 1,000 feet AGL or lower levels would not only increase the likelihood of encounters with obstacles but also diminish safety margins when operating in controlled environments. Similarly, aiming for altitudes like 1,500 feet or even 3,000 feet AGL does not align with the specific regulatory framework that dictates the minimum safe altitude at which VFR operations should be conducted in controlled airspace.