Final answer:
An indication of an aircraft's certification for overwater operations is typically found in the AFM or certification documents, noting the ability to operate safely 60 minutes from an Adequate Airport. This certification considers engine reliability, navigation systems, emergency systems, and required training for such operations.
Step-by-step explanation:
An indicator that an aircraft is certified for overwater operations up to 60 minutes (Single-Engine still air) out from an Adequate Airport can be found in the aircraft's certification documents or specified in the Airplane Flight Manual (AFM). For many aircraft, this capability is delineated under Extended-range Twin-engine Operational Performance Standards (ETOPS) for twin-engine aircraft, or a similar certification for single-engine planes, often termed single-engine overwater operations certification.
To achieve this certification, aircraft are evaluated for their engine reliability, navigation and communication systems, crew training, and the presence of life-saving equipment. This implies that the plane has redundant systems and safety features that allow it to operate safely with one engine over water, away from an adequate landing spot. The ETOPS rating or equivalent single-engine certification details the maximum time that an aircraft can be from a suitable airport, which includes considerations like weather conditions, the aircraft's glide range in the event of engine failure, emergency systems, and the availability of alternate airports.