Foreign firms owned or controlled by United States persons are authorized to engage in transactions ordinarily incident to the bunkering of vessels and to the fueling of aircraft owned or controlled by, or chartered to, Cuba or nationals thereof.
31 C.F.R. §515.558
50 U.S.C. App. 5(b); 22 U.S.C. 2370(a) ; E. O. 9193, 3 CFR 1943 Cum. Supp.; Treas. Dept. Order No. 128, 32 FR 3472