Such political subdivisions, acting singly or jointly, are hereby authorized and empowered to enter into contracts and agreements with the federal government or agencies thereof for the acquisition, planning, construction, enlargement, improvement, maintenance, equipment, or operation of airports and other air navigation facilities: Provided, That where such acquisition, planning, construction, improvement, enlargement, maintenance, equipment or operation is financed wholly or partly with federal moneys, said political subdivision of this state may let contracts in the manner prescribed by the federal authorities, acting under the laws of the United States, and any rules or regulations made thereunder.