Single Pilot
Remember, the SR-71 (Mach 3.2, 80,000 feet) with a MTOW of 170,000 lbs. was the largest single pilot airplane flown. B-58 Hustler a close second. The Avro Lancaster was also single pilot.
Single pilot ops in many business jets and turboprops involves the systems layout, redundancy and the ability of the pilot to continue to fly after a system failure. For example, radio communications; headset, or ICS failure, ability to continue to use at least one VHF radio.
For example, by modification of the landing gear handle, the DC-3 has been approved for single pilot operations.