Final answer:
ATC controllers, depending on the aviation authorities' regulations, may be considered for waivers at any certification level, but the primary concern is to ensure safety and operational effectiveness.
Step-by-step explanation:
The question pertains to which ATC controllers may be considered for a waiver of standards. The options given are fully certified, partially certified, and non-certified controllers. In the context of air traffic control (ATC), certification levels refer to the qualification and experience of the controller. Depending on the policies and regulations in place, a waiver of standards may be granted to controllers who do not meet all the qualification criteria. This typically involves an evaluation of the individual's experience, skills, and sometimes extenuating circumstances.
Air traffic controllers have highly responsible roles where the safety of passengers and the efficiency of the airspace are paramount. Therefore, while all levels of certification could be considered for a waiver, it is critical to ensure that any such waiver does not compromise safety and operational effectiveness. The decision to grant a waiver would be carefully assessed on a case-by-case basis by the relevant aviation authorities.