The Assistant Secretary for Policy, Plans and International Affairs (Assistant Secretary), in coordination with the General Counsel and the Federal Aviation Administrator (Administrator), on complaint of any U.S. flag air carrier or on their own initiative, shall investigate: (a) Instances of alleged excessive or otherwise discriminatory user charges or (b) discriminatory or unfair competitive practices to which U.S. flag air carriers are subjected by a foreign government or other foreign entity. Excessive or otherwise discriminatory charges include, but are not limited to, unreasonable landing fees, unreasonable monopoly ground handling fees and unreasonable air navigation charges. Discriminatory or unfair competitive practices include, but are not limited to, unreasonably differentiated fuel allocations, cargo, charter or currency restrictions and inferior monopoly ground handling services.