“The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.” This is the first paragraph of Section 91.3 of the Federal Aviation Regulations.
The next paragraph gives the same person room to act. In an in-flight emergency that requires immediate action, the pilot in command may depart from any rule of that part as far as the emergency requires. Afterward, the pilot must send a written report if the FAA asks for one.
The rule speaks of one person. The pilot in command is both “directly responsible” and “the final authority.”