I knew a guy who was a 737 first officer and happened to have a 737 type rating. He decided he would log the legs he flew as PIC time.
My interpretation is that 2 people can't log pic time for the same flight. (I'm talking 121 line flying) This guy wasn't the captain, didn't sign the flight release and wasnt' responsible for the flight yet he thought it was his right to log his legs as PIC time.
Errrr.......almost. He can log PIC time IAW part 61, because the section of part 61 that deals with logging flight time does not differentiate between flying under FAR 91/121/135, etc. Think of it this way..........
The 737 type rated FO (no ATP) logs his legs as PIC. Fine, ok. He then goes for an ATP checkride and presents his logbook to Mr. FAA inspector/DPE who then looks it over. All his PIC time logged in the 73 was as the sole manipulator of the controls in an aircraft for which he had the appropriate category/class/type ratings. FAA inspector/DPE is happy and the 737 FO gets his ATP.
Fast forward now to the same 737 FO's interview with Southwest. For the airlines, they only consider FAR part 1 PIC time, which is defined as the person who was directly responsible for, and the final authority to, the safe operation of the aircraft. Since the 737 FO was not acting as the PIC for those flights (even though he was perfectly legal to LOG PIC time), Southwest disregards those hours and sends him home with no job offer.
The FAR's rules for logging PIC, and what the airlines CONSIDER PIC time, differ. In part 61, it says you can log it if you're..........
1. Acting as CFI
2. Sole manipulator of controls on a/c for which you have appropriate category/class/type ratings
3. Acting PIC (IAW FAR 1; definition of PIC which is pilot responsible for a flight, etc, ) of a flight requiring more than one pilot under the regulations for which the flight is conducted (this is what allows a safety pilot and the guy under the hood to log PIC)
4. ATP acting as PIC of a flight requiring ATP certificate to be PIC (121/135 flight)
5. Flying solo
Under any of the five examples above, a pilot can log PIC time to meet the aeronautical experience requirements for a certificate or rating under part 61. And it in no way precludes 2 pilots from logging PIC on one flight. But just because it meets the above requirements does not mean SWA/FDX/UPS/etc. have to accept it for their hiring criteria. For the these carriers, only hours logged as the pilot directly responsible for, and the final authority to, the safe operation of the aircarft (signed for the aircraft, acted as PIC, etc.) count to meet their minimums. Hope this helps.