Delta Air Lines said it bought seven more MD-90 jets from Japan Airlines to replace older planes.

Atlanta-based Delta will get the planes between October 2012 and March 2013, and plans to begin flying all of them by the end of 2013.

The purchase is in addition to the nine MD-90s Delta bought from Japan Airlines last year. Delta said it has acquired 49 MD-90s in the past three years, and with the latest purchases it will eventually have a total of 65.

In the face of high fuel prices and an uncertain economy, Delta said it's part of a strategy to use the most efficient aircraft whenever possible.