(1) That during the existence of any emergency declared by the President or the Congress, the Government shall have the right without charge except as indicated below to the full, unrestricted possession, control, and use of the landing area, building areas, and airport facilities or any part thereof, including any additions or improvements thereto made subsequent to the declaration of the airport property as surplus: Provided, however, That the Government shall be responsible during the period of such use for the entire cost of maintaining all such areas, facilities, and improvements, or the portions used, and shall pay a fair rental for the use of any installations or structures which have been added thereto without Federal aid.

(2) During any national emergency declared by the President or by Congress, the United States shall have the right to make exclusive or nonexclusive use and have exclusive or nonexclusive control and possession, without charge, of the airport at which the surplus property is located or used or of such portion thereof as it may desire: Provided, however, That the United States shall be responsible for the entire cost of maintaining such part of the airport as it may use exclusively, or over which it may have exclusive possession and control, during the period of such use, possession, or control and shall be obligated to contribute a reasonable share, commensurate with the use made by it, of the cost of maintenance of such property as it may use nonexclusively or over which it may have nonexclusive control and possession: Provided further, That the United States shall pay a fair rental for its use, control, or possession, exclusively or nonexclusively, of any improvements to the airport made without U.S. aid.