The Rescue Phoenix is the main base of Rescue Force. It is a giant structure that resembles a standard command center in Fortress Mode, while it takes the form of a plane in Flight Mode.
This is Rescue Phoenix's default mode. It is the center of the Rescue Force headquarters, and is where the main room shown in the series is located.
When getting ready for takeoff, Rescue Phoenix extends various parts to become a giant plane. From here, Rescue Striker would be connected to it, and any additional vehicles would be stored inside it before shooting off towards the disaster.
Spiral Catapult Mode
With the creation of Core Striker Max, the show introduced Phoenix's spiral catapult mode, which created, as the name implies, a spiral road that Striker would ride off of before being catapulted out into action.