Which fixed-wing aircraft has the highest number of required flight crew members? Most modern airliners require two pilots to operate. Older airliners require a flight crew of three: two pilots plus one flight engineer.

Has there ever been an aircraft where the number of required flight crew members is extraordinarily high, for example five or six?

To clarify the question:


"required flight crew member" is the number required by relevant regulations, not the number needed to physically operate the plane. If that number is not met, the plane could not legally have taken off
gunners / weapon operators of military aircraft who are not necessary for a safe flight are not included
flight attendants are not included
The Antonov An-225 Mriya requires a crew of six- you have the pilot, copilot, 2 flight engineers, navigator and a communications specialist/radio operator.



An-225 cockpit; image from sas1946.com