Lion Air introduced the Boeing 737-900ER into commercial passenger service in 2007.
The Indonesian airline received the first 737-900ER and began operating the type in April 2007. The aircraft was the extended-range version of the 737-900, with additional features such as an auxiliary fuel tank option, strengthened landing gear, and redesigned exit arrangements that allowed higher passenger capacity.
Lion Air became a major operator of the 737 Next Generation family as it expanded across Indonesia and other Asian markets. The 737-900ER was designed to compete with the Airbus A321, offering a larger capacity than the 737-800 while retaining the 737 family's common cockpit and maintenance advantages.
The 737-900ER is distinct from the later 737 MAX 9. Although the two aircraft occupy a similar size category, the MAX 9 belongs to Boeing's newer 737 MAX generation and uses different engines and aerodynamic improvements.