During a thorough review of space shuttle Discovery's readiness for flight, NASA managers decided Friday that more data and possible testing are required before launching the STS-119 mission to the International Space Station.

Engineering teams have been working to identify what caused damage to a flow control valve on shuttle Endeavour during its November 2008 flight.

"We need to complete more work to have a better understanding before flying," said Bill Gerstenmaier, associate administrator for Space Operations at NASA Headquarters in Washington who chaired Friday's Flight Readiness Review. "We were not driven by schedule pressure and did the right thing. When we fly, we want to do so with full confidence."

The shuttle has three flow control valves that channel gaseous hydrogen from the main engines to the external fuel tank. Teams also have tried to determine the consequences if a valve piece were to break off and strike part of the shuttle and external fuel tank.

The Space Shuttle Program has been asked to develop a plan to inspect additional valves similar to those installed on Discovery. This plan will be reviewed during a meeting on Wednesday, Feb. 25. Afterward, the program may consider setting a new target launch date.

For more information about the Space Shuttle Program, including a fact sheet about the flow control valves, visit: