The four Boeing 757's are narrow-body 200-passenger planes, with a total value of about $200 million.
When the modifications are completed, 78 percent of American's narrow-body planes will have at least 16 first-class seats.
It also only has two rows of seats, which makes it a narrow-body plane.
Boeing said yesterday that demand for its narrow-body planes, especially the latest version of the 737, the world's most popular commercial jetliner, remained strong.
It has been estimated that narrow-body planes will constitute 60 to 65 percent of the jetliners to be sold over the next 19 years.
The typical narrow-body plane at Pan Am flies six hours a day, going back and forth between just two cities.
It only has two rows of seats, which means it is a narrow-body plane.
Despite United's service upgrade, its 757 is a narrow-body plane.
He could also pick up planes from Eastern's fleet to strengthen Northwest's domestic fleet, which has many aging narrow-body planes.
Aircraft brokers agree on many of the reasons for the glut in the market for used narrow-body planes.