What is generally required of pilots when flying in controlled airspace?

Pilots flying in controlled airspace are typically required to have their aircraft equipped with a mode S transponder. This type of transponder allows air traffic control (ATC) to identify and track aircraft, which enhances situational awareness and safety within crowded airspace. The mode S transponder provides information such as the aircraft's altitude and allows for more precise communication and monitoring by ATC.

While filing a flight plan is often necessary, especially for IFR (Instrument Flight Rules) operations, it is not universally required for all flights in controlled airspace. Similarly, ATC does assign specific altitudes to pilots, but this is part of the ATC service rather than a baseline requirement for entering controlled airspace. Prioritizing fuel efficiency is important in aviation but is not a specific regulatory requirement when it comes to controlled airspace operations. Thus, having a mode S transponder is a fundamental requirement that directly influences the ability to operate safely and effectively in controlled airspace.