Taxation of international shipping and air transport profits: source state primary, limited secondary taxation with mandated reduction. Profits from operation of ships or aircraft in international traffic are taxable only in the enterprise's Contracting Party, except that profits derived in the other Contracting Party from ship operations may be taxed there subject to a prescribed reduction; the rule also covers participation in pools, joint businesses and international operating agencies and expressly includes revenues from transport and incidental services, interest tied to operations, and incidental container leasing.