Original sentence: The slow and unpressurized DC-3s and Martin 2-0-2s were of an earlier generation and were now showing their age, so in 1960 a gradual phase-out of the venerable planes began; the last of them were gone from Pacific's fleet by mid-1964.To better reflect the territory covered by their flights, the company name was changed to Pacific Air Lines on May 6, 1958
Edited sentence: The last of the Martin 2-0-2s was retired in March 1964.The reliable but slow and unpressurized DC-3s were of a mid-1930s design and were now showing their age, so in 1960 a gradual phase-out of the venerable planes began; the last of thirteen operated were gone from Pacific's fleet by mid-1964.To better reflect the territory covered by their flights, the company name was changed to Pacific Air Lines on March 6 1958