Under which circumstances are you required to communicate with ATC?

When operating under Part 135 regulations, communication with Air Traffic Control (ATC) is essential for maintaining safety and efficient operation in the airspace system. The requirement to communicate with ATC can arise in various scenarios.

You are obligated to communicate with ATC when requested, as this ensures compliance with airspace regulations and helps ATC manage traffic effectively. Additionally, unfavorable weather conditions necessitate communication to ensure that ATC is aware of your situation and can provide guidance or support, particularly if you're considering changes to your flight plan due to the weather.

Moreover, crossing a compulsory reporting point requires communication to provide ATC with your position updates. This aids in the situational awareness and overall management of air traffic in the area, especially in busy airspaces.

Thus, all of these circumstances require you to communicate with ATC to ensure safety, compliance, and coordination within the air traffic system.