Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 112; Flight Crew Total 3838; Flight Crew Type 2493
Physiological - Other; Situational Awareness; Communication Breakdown; Other / Unknown
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
General None Reported / Taken
Human Factors; Environment - Non Weather Related; Company Policy
On the morning of an international departure that was scheduled to depart later that evening; the Captain emailed and informed both FOs of how the flight would be conducted in regard to face masks.  During the pre-flight phase; the #2 FO challenged the decision and said he was walking off the trip unless the Captain agreed to wear a mask whenever he was on the Flight Deck.  In an effort to maximize safety and also to address the #2 FO's concerns; the Captain offered the solution that he would wear a mask during cruise; whenever the #2 was performing his relief duties; but; with safety concerns about glasses fogging and hindered communications during critical phases of flight; said that #2 could sit in the cabin rest seat during those phases if it would make him more comfortable (since masks would not be worn).  The Captain believed this was 'legal;' since an #2 actually wasn't required by the FARs on the planned 6 hour and XX minutes flight and was also the safest option since; if the #2 dropped the trip; the flight would likely be sent un-augmented with zero inflight rest periods then available to the 'flying' pilots. The #2 agreed with this solution and the flight departed.Prior to the later descent; the #2 stated that he believed that an FAR's had been violated by him not being in the cockpit for takeoff.  He said that he would be in the cockpit for descent and Captain said he was welcome to be there but reiterated that masks would not be worn during critical phases of flight.  The #2 did then come up for the descent and landing.After the aircraft was parked and debrief conducted; #2 said he would be submitting a report over his belief that an FAR was violated by him not being in the cockpit for takeoff and departure.The Captain and #1 FO are not aware of any 'violations' of FAR's in this instance but decided to report the incident in case there's something they are not aware of.
During takeoff; the #2 FO stayed in overhead flight crew rest area instead of on the Flight Deck.  Erroneously thinking his presence was not required on Flight Deck on takeoff. Captain and #2 chose that course of action; as #2 wasn't comfortable with staying on Flight Deck with the Captain who had a cough. Captain was unable to wear a mask due to fogging of glasses.
Air Carrier flight crew reported they had an agreement between themselves regarding face mask policy on the flight deck and may have violated FAR/SOP policy.