((a)) ** .—** To maintain a safe and efficient nationwide system of public-use airports that meets the present and future needs of civil aeronautics, the Secretary of Transportation may make project grants under this subchapter from the Airport and Airway Trust Fund.

((b)) ** .—** The Secretary may incur obligations to make grants from amounts made available under as soon as the amounts are apportioned under section 47114(c) and (d)(2) of this title.

((c)) ** .—** After , the Secretary may not incur obligations under subsection (b) of this section, except for obligations of amounts—

((1)) remaining available after that date under ; or

((2)) recovered by the United States Government from grants made under this chapter if the amounts are obligated only for increases under section 47108(b)(2) and (3) of this title in the maximum amount of obligations of the Government for any other grant made under this title.