Marty Shapiro writes:

Public Aircraft:

(1) An aircraft used only for the United States Government; an aircraft
owned by the Government and operated by any person for purposes related to
crew training, equipment development, or demonstration; an aircraft owned
and operated by the government of a State, the District of Columbia, or a
territory or possession of the United States or a political subdivision of
one of these governments; or an aircraft exclusively leased for at least 90
continuous days by the government of a State, the District of Columbia, or
a territory or possession of the United States or a political subdivision
of one of these governments.

This definition excludes cities, and therefore excludes most police
departments.

As a mater of regulation, pilots of public aircraft do not have to
have a pilot's certificate.

But cops are not pilots of public aircraft, generally speaking, based
on the definition given above. They are civilian employees of cities,
not employees of the U.S. government or its States, territories, or
possessions, and their aircraft are presumably in the same category.

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