A gas turbine engine incorporating a starter mounted on the gear box is disclosed. The gas turbine engine includes an AGB gear housing mechanically connected with an engine shaft for driving auxiliary machines and an air starter mounted on the housing, the starter and housing enclosures being in communication such that the lubricating oil of the starter should be distributed from the AGB housing. The oil enclosure of the starter is pressurized by a source of air, being independent from the AGB housing. Advantageously, the pressurization air is taken from a pressurization enclosure of an engine bearing.