For purposes of this section, the term covered aircraft means an aircraft operated under part 121 of title 14, Code of Federal Regulations. 341. Part 135 pilot supplemental oxygen requirement Not later than 1 year after the date of enactment of this section, the Administrator shall issue a notice of proposed rulemaking concerning whether to revise the requirements under paragraphs (3) and (4) of section 135.89(b) of title 14, Code of Federal Regulations, to only apply to aircraft operating at altitudes above flight level 410. In the notice of proposed rulemaking, the Administrator shall consider applicable safety data and risks, including in relation to applicable incidents and accidents, as well as the investigations and recommendations of the National Transportation Safety Board. 342. Crewmember pumping guidance (a) In general Not later than 180 days after the date of enactment of this section, the Administrator shall issue guidance to Part 121 air carriers relating to the expression of milk by crewmembers on an aircraft during non-critical phases of flight, consistent with the performance of the crewmember's duties aboard the aircraft. The guidance shall be equally applicable to any lactating crewmember. In developing the guidance, the Administrator shall— (1) consider multiple methods of expressing breast milk that could be used by crewmembers, including the use of wearable lactation technology