Scaled Composites White Knight Two

The Scaled Composites Model 348 White Knight Two (WK2) is a quadjet cargo aircraft that was used to lift the SpaceShipTwo (SS2) spacecraft to release altitude. It was developed by Scaled Composites from 2007 to 2010 as the first stage of Tier 1b, a two-stage to suborbital-space crewed launch system. WK2 is based on the mothership to SpaceShipOne, White Knight, which itself was based on Proteus.

The aircraft was designed for multi-purpose use, with an "open architecture" intended to enable it to operate as a zero-g aircraft for passenger training or microgravity science flights, to perform other high-altitude testing missions, or to launch payloads other than SpaceShipTwo. Another idea is to add a carbon-composite water tank to make it a forest fire water bomber.

The first White Knight Two was unveiled on July 28, 2008, and first flew on December 21, 2008; it is named VMS Eve after Richard Branson's mother Eve Branson. The second was expected to be named VMS Spirit of Steve Fossett after Branson's close friend Steve Fossett, who died in an aircraft accident in 2007. As of 2024, it was not clear whether SS2 and WK2 vehicles beyond VSS Enterprise, VSS Unity and VMS Eve will be built.