(1) During the six financial years ending on 31st March 1972, the Treasury may, subject to subsection (2) below, from time to time issue out of the National Loans Fund sums not exceeding in the aggregate four hundred and thirty million pounds, to be applied as appropriations in aid of moneys provided by Parliament for those years for defraying expenditure by the Ministry of Defence and the Ministry of Aviation—
(a) in the purchase from the Government of the United States of America of military aircraft, or parts, equipment or other articles for, or for use in connection with, military aircraft, or
(b) in making payments to that Government in respect of costs incurred by them in connection with any aircraft, equipment or other articles so purchased, including in particular costs of development and testing and of training persons in their operation or maintenance.
(2) The sums issued for any year under the preceding subsection shall not, in the case of either Ministry, at any date exceed in the aggregate the total amount proposed to be so issued to defray their expenditure on the matters referred to in that subsection by the estimates upon which the House of Commons has, before that date, resolved to grant sums to Her Majesty to defray such expenditure for that year.
(3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .