When starting the aircraft, the power control lever should be __________.

The correct answer is that the power control lever should be pushed forward until a green ST READY message is illuminated on the EICAS display. This step is crucial in the aircraft start procedure because the ST READY message indicates that the engine is configured and ready to be started safely, ensuring that all required conditions have been met for ignition to occur.

Pushing the power control lever to the START/IDLE detent is part of the process, but the specific action of reaching the ST READY state confirms the system is prepared for the next phase of engine start. This ensures that the engine starts efficiently and effectively, minimizing risks associated with starting the engine in an improper configuration.

In contrast, while the IGN SEL message is related to the ignition process, it pertains specifically to the selection of ignition sources rather than confirming readiness for engine start. Thus, it doesn't directly pertain to the immediate action of starting the aircraft engine.