Just for you guys, starting Oct 20th. The new 61.51:

"A sport, recreational, private, commercial, or airline transport pilot may log pilot in command flight time for flights-

(iv) When the pilot performs the duties of pilot in command while under the supervision of a qualified pilot in command provided—
(A) The pilot performing the duties of pilot in command holds a commercial or airline transport pilot certificate and aircraft rating that is appropriate ...;
(B) The pilot performing the duties of pilot in command is undergoing an approved pilot in command training program that includes ground and flight training on the following areas of operation—
(1) Preflight preparation;
(2) Preflight procedures;
(3) Takeoff and departure;
(4) In-flight maneuvers;
(5) Instrument procedures;
(6) Landings and approaches to landings;
(7) Normal and abnormal procedures;
(8) Emergency procedures; and
(9) Postflight procedures;
(C) The supervising pilot in command holds—
(1) A commercial pilot certificate and flight instructor certificate, and aircraft rating that is appropriate ...; or
(2) An airline transport pilot certificate and aircraft rating that is appropriate ...; and
(D) The supervising pilot in command logs the pilot in command training in the pilot's logbook, certifies the pilot in command training in the pilot's logbook and attests to that certification with his or her signature, and flight instructor certificate number."

I highlighted the bold for you.