Pan American Airlines. Model II, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model III, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model IX, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model VI, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model VII, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model XII, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model XIII, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model XIX, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model XV, Gottscho-Schleisner Collection (Library of Congress)

Pan American Airlines. Model XXI, Gottscho-Schleisner Collection (Library of Congress)