Russia delivered advanced air defence equipment to Turkey on Saturday.
Russian air force AN-124 planes offloaded equipment at the Murted air base near the Turkish capital Ankara.
Washington tried for months to prevent the deal.
U.S. officials warned that Turkey would be thrown off the F-35 programme and face sanctions under U.S. legislation.
Turkish Defence Ministry said, Turkey remains under a serious air and missile threat and that purchase of S-400 defense systems was not an option but rather a necessity.
A further delivery of 120 guided missiles would be carried out at the end of the summer.
