Every airline ticket has a security charge tacked on to it which could just be diverted to the private security contractor.
§ 1542.105 Approval and amendments.
....
(b) Amendment requested by an airport operator. Except as provided in § 1542.103(c), an airport operator may submit a request to the designated official to amend its security program, as follows:
(1) The request for an amendment must be filed with the designated official at least 45 days before the date it proposes for the amendment to become effective, unless a shorter period is allowed by the designated official.
(2) Within 30 days after receiving a proposed amendment, the designated official, in writing, either approves or denies the request to amend.
(3) An amendment to a security program may be approved if the designated official determines that safety and the public interest will allow it, and the proposed amendment provides the level of security required under this part.
(4) Within 30 days after receiving a denial, the airport operator may petition the Administrator to reconsider the denial.
(5) Upon receipt of a petition for reconsideration, the designated official either approves the request to amend or transmits the petition within 30 days of receipt, together with any pertinent information, to the Administrator for reconsideration. The Administrator disposes of the petition within 30 days of receipt by either directing the designated official to approve the amendment or affirming the denial.
§ 1542.213 Training.
(a) Each airport operator must ensure that individuals performing security-related functions for the airport operator are briefed on the provisions of this part, Security Directives, and Information Circulars, and the security program, to the extent that such individuals need to know in order to perform their duties.
(b) An airport operator may not authorize any individual unescorted access to the secured area or SIDA, except as provided in § 1542.5, unless that individual has successfully completed training in accordance with TSA-approved curriculum specified in the security program. This curriculum must detail the methods of instruction, provide attendees with an opportunity to ask questions, and include at least the following topics—
(1) The unescorted access authority of the individual to enter and be present in various areas of the airport;
(2) Control, use, and display of airport-approved access and identification media;
(3) Escort and challenge procedures and the law enforcement support for these procedures;
(4) Security responsibilities as specified in § 1540.105;
(5) Restrictions on divulging sensitive security information as described in part 1520 of this chapter; and
(6) Any other topics specified in the security program.
https://www.ecfr.gov/current/title-49/subtitle-B/chapter-XII/subchapter-C/part-1542
NOTE: Law is complex. That may not be all that matters.
There anbout about 20 airports in the USA that use private security. One of them is San Francisco international. They must follow the training rules and guidelines of TSA but are not government employees. There is no reason that they need to be government employees.
“if any airport was allowed to privatize security to replace TSA”
TSA is to airport security what inner city public schools are to education.