Transportation Secretary Samuel K. Skinner seems ready to pick a fight with Congress over who makes U. S. aviation policy. The blowup could come if Skinner, as expected, approves the sale of Trans World Airlines Inc.'s U. S.-London routes to American Airlines Inc. Legislators, including Senate Commerce Committee Chairman Ernest F. Hollings (D-S. C.) and ranking GOP member John C. Danforth (Mo.), fear increased concentration in the industry and want to block the sale. Congress is also unhappy Skinner got few concessions when he gave expanded U. S. landing rights to British carriers.