Part 135

Part 135 governs commercial on-demand operations — charter and air-taxi flights carrying passengers or cargo for hire. It imposes stricter requirements than private Part 91 flying on crew training and duty times, maintenance, and operational control. When you charter a jet in the US, you're flying on a Part 135 certificate.

Why it matters: Part 135 is the certification regime for on-demand commercial operations — charter — in the United States, with close analogues elsewhere. It imposes operational control, crew duty and rest limits, training and checking, maintenance standards and regulatory oversight beyond private flying, which is precisely why charter customers benefit from it.

For an owner, placing an aircraft on a charter certificate converts idle time into revenue but brings the aircraft under the operator's commercial standards — additional inspections, conformity requirements and shared control of scheduling. The revenue is real; so is the loss of flexibility and the added wear.