41 CFR § 102-33.55
Are there restrictions on acquiring Government aircraft?
June 9, 2020
Yes, you may not acquire—
(a) More aircraft than you need to carry out your official business;
(b) Aircraft of greater size or capacity than you need to perform your Governmental functions cost-effectively; or
(c) Federal aircraft that Congress has not authorized your agency to acquire or Federal aircraft or commercial aircraft and services for which you have not followed the requirements in OMB Circulars A-76 and A-11 (available at http://www.whitehouse.gov/omb).