WhiteKnightTwo's fifth flight has been 'a great success', say Virgin Galactic.

Mothership Eve took to the skies on 20 May and tested the full cabin pressurisation system and environmental control systems.

She was in the air for around three hours, and went up to 20,000 feet. The flight was rounded off with an emergency landing drill test involving the manufacturers Scaled Composites and Mojave Air and Space Port..

'All in all it paves the way for the next flights which can start to push the envelope on altitude etc,' said Virgin Galactic President Will Whitehorn to Rob Coppinger at Hyperbola.

Scaled Composites are now posting up summaries of flight test results on their own site. They note that WhiteKnightTwo shares many system components with SpaceShipTwo, cabon and environmental control systems among them.

'Thus the flight test program of WK2 includes many tests that focus on SS2 systems qualification and maturity,' they say.