Just a week after the first in-flight venting of its nitrous system, Virgin Galactic’s SpaceShipTwo has made an even more spectacular step on the way to its first powered flight. The craft's 25th glide flight on April 12 saw oxidizer flow through the craft’s propulsion system and expelled through the nozzle at its rear in what is known as a “Cold Flow” procedure.

This was the first time the test has been conducted in flight, with the resulting oxidizer contrail creating a stunning spectacle in the skies above the Mojave Desert. Virgin Galactic says the flight provided the first taste of what SpaceShipTwo will actually look like as it makes its way to space.

Aside from the impressive visual display, the company says the successful “Cold Flow” test indicates that the system is flight ready. Actually igniting the rocket is all that remains to complete the profile of the upcoming first powered flight.

With that impending flight to be the first time that the spacecraft will be flown with all systems installed and operational, Virgin Galactic says that in many ways it will be the most significant milestone to date. The company was initially aiming to conduct the first powered flight by the end of 2012, but looks on track to achieve this within the coming months.