The Administrator may suspend the effectiveness of any allocation prescribed in Sec. 93.123 and the reservation requirements prescribed in Sec. 93.125 if he finds such action to be consistent with the efficient use of the airspace. Such suspension may be terminated whenever the Administrator determines that such action is necessary for the efficient use of the airspace. [Doc. No. 9974, 35 FR 16592, Oct. 24, 1970, as amended by Amdt. 93-21, 35 FR 16636, Oct. 27, 1970; Amdt. 93-27, 38 FR 29464, Oct. 25, 1973]