Northwest had been the first United States airline to take delivery Sending of the Super Electra , but sold Commerce_sell most of its remaining Presence Electra fleet in 1939 after three subsequent accidents Catastrophe called Name_conferral the airworthiness and commercial potential of the aircraft into question .

A doubler plate on the rear bulkhead of the plane had been improperly repaired Recovering , compromising Influence the plane 's airworthiness .

These accidents , as well as two others which befell Self_motion Northwest Airlines Super Electras in 1938 , called into question the airworthiness and commercial potential of the model .