What is an MEL?

An MEL, or Minimum Equipment List, is a critical document that is part of an aircraft's operating procedures. It specifies the equipment and systems that must be functional for an aircraft to be considered airworthy and to operate safely. The MEL allows pilots and operators to understand which equipment can be inoperative while still safely conducting flights, provided that all necessary steps are taken to ensure safety and compliance with regulations.

The MEL is particularly important for managing operational limitations when certain equipment is down, allowing airlines to maintain service continuity without compromising safety. Each aircraft has its own MEL tailored to its specific systems and type, facilitating a standardized approach to safety management in aviation operations.

This definition aligns directly with the choices of the question, as it clearly identifies the essential nature of the Minimum Equipment List in aviation safety and regulation compliance.