The airline transport pilot and two passengers, one of whom was pilot-rated, were conducting a cross-country flight in dark, night visual conditions. During an en route climb to the assigned cruise altitude, the airplane experienced a loss of engine power about 6,600 ft above ground level (agl). The pilot identified a diversionary airport located about 4 miles northeast of the airplane's position and subsequently established a course toward that airport. The air traffic controller immediately informed the pilot that the airport was closed. However, based on the pilot's stated intention to divert to the airport, the controller provided radar vectors to assist the pilot. The airplane subsequently overflew the airport about 3,000 ft agl. However, instead of circling the airport, the pilot continued about 1 1/2 miles north and entered a right gliding turn until the airplane impacted trees and terrain about 2 miles north of the airport.A postaccident airframe examination did not reveal any anomalies consistent with an airframe structural failure or a malfunction of the flight control system. An engine examination revealed that the No. 4 piston had failed. Specifically, the perimeter of the No. 4 piston crown had separated, resulting in the separation of the upper compression ring and compression ring insert. Metallurgical examination determined that the piston failure was caused by the disbonding of the upper piston ring insert from the piston body. Lead deposits were present on parts of the piston body that formed an interface with the insert. The deposits were abraded in areas exposing the underlying piston material. The abraded areas where the deposits had been worn away could only have occurred if the upper piston ring insert had disbonded from the piston body before the piston failed. The disbonding of the insert was likely caused by a manufacturing anomaly; however, due to the extensive damage to the piston and the insert, it was not possible to determine with any more precision where the failure started or the nature of the defect that might have caused it.An airplane performance study revealed that no airports other than the diversionary airport were within the power-off glide range of the airplane at the time of the loss of engine power. Thus, the location of the airplane at the time of the loss of engine power presented the pilot with limited options for a forced landing. Furthermore, the pilot's ability to discern a suitable off-airport landing area was hindered by the Page 2 of 11 CEN18FA053dark night lighting conditions. Although, an interstate highway was below the airplane, attempting to execute a forced landing on an unlighted roadway at night presented significant hazards. In contrast, approach paths to an airport are generally free of obstructions. Therefore, the pilot's decision to alter course toward the diversionary airport, even though it was closed and unlighted, was understandable. However, once the airplane was positioned over the airport, the pilot did not circle but continued to fly north into an area with more limited opportunities for a successful forced landing.A review of the available medical information did not reveal the presence of any condition or medication that would have led to an incapacitation or impairment of the pilot. However, the pilot was likely fatigued at the time of the accident due to the length of time he had been awake, and the significant amount of flight time completed on the day of the accident. This may have narrowed the pilot's attention during the emergency. Additionally, situational stress imposed by the engine failure and the necessity to find a forced landing site in dark night conditions further reduced the pilot's ability to maintain situational awareness.The pilot-rated passenger's medical history included conditions and medications that, while unlikely to cause any sudden incapacitation, could potentially be impairing. However, the investigation was unable to determine the extent of impairment, if any, that might have been present at the time of the accident.