Mont. Code Ann. § 67-1-104

67-1-104 . Governmental nature of aeronautical functions. The acquisition of lands for establishing airports or other air navigation facilities; the acquisition of airport protection privileges; the acquisition, establishment, construction, enlargement, improvement, maintenance, equipment, and operation of airports and other air navigation facilities, whether by the state separately or jointly with a municipality; the assistance of this state in that acquisition, establishment, construction, enlargement, improvement, maintenance, equipment, and operation; and the exercise of any other powers granted to the department are public and governmental functions exercised for a public purpose and as a matter of public necessity; and such lands and other property and privileges acquired and used by the state in the manner and for the purposes enumerated in this title are acquired and used for public and governmental purposes and as a matter of public necessity.