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Not only must they purchase ( or lease ) new airliner bodies and engines regularly , they must make major long-term fleet decisions with the goal of meeting the demands of their markets while producing a fleet that is relatively economical to operate and maintain ; comparably Southwest Airlines and their reliance on a single airplane type ( the Boeing 737 and derivatives ) , with the now defunct Eastern Air Lines which operated 17 different aircraft types , each with varying pilot , engine , maintenance , and support needs .
 Southwest Airlines, Eastern Air Lines
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Southwest Airlines, Eastern Air Lines