The 690A, first produced in 1973, represented a significant advancement for turboprop Twin Commander aircraft. This model used the more powerful 251K variant of the AiResearch TPE331 power plant and Hartzell propellers. Airframe changes included an increase of 30 inches at the center wing section, increased rudder area, enlarged dorsal fin and longer tail cone. These changes allowed for a gross weight rating of 9,600 and baggage capacity of 600 lbs., the highest for a Twin Commander. Other changes such as the addition of a heated windshield, increased cabin pressure differential and standard de-icing equipment, changed the maximum ceiling rating from 25,000 feet to 31,000 feet.