SEATTLE, United States (AP) -- Boeing will decide on a plan to replace its popular 737 aircraft by 2012 at the latest, a spokeswoman told The Associated Press Thursday.

Last year, the company started seriously considering a successor for the 737, for which Boeing has won more than 6,000 orders since its 1967 debut.

Sandy Anger, a Boeing spokeswoman, said the company "must ensure it has the right set of breakthrough technologies in engines, aerodynamics, materials and other systems" to top the 737's efficiency.

Anger said Boeing estimates it will be ready with a replacement for the 737 "sometime in the middle of the next decade -- give or take a couple of years."

The 737 competes with Airbus' hot-selling A320, which went into service in 1988. Toulouse, France-based Airbus says it has sold more than 5,500 A320s