1) A party is not liable for a failure to perform any of his
obligations if he proves that the failure was due to an
impediment beyond his control and that he could not
reasonably be expected to have taken the impediment into
account at the time of the conclusion of the contract or to have
avoided or overcome it or its consequences.
(2) If the party’s failure is due to the failure by a third person
whom he has engaged to perform the whole or a part of the
contract, that party is exempt from liability only if—
(a) he is exempt under the preceding paragraph; and
(b) the person whom he has so engaged would be so exempt
if the provisions of that paragraph were applied to him.
(3) The exemption provided by this article has effect for the
period during which the impediment exists.
(4) The party who fails to perform must give notice to the other
party of the impediment and its effect on his ability to
perform. If the notice is not received by the other party within
a reasonable time after the party who fails to perform knew or
ought to have known of the impediment, he is liable for
damages resulting from such non-receipt.
(5) Nothing in this article prevents either party from exercising
any right other than to claim damages under this Convention