NASA announced last week that it is delaying the flight of STS-119 by at least a week. They had replaced fuel valves and are not happy with the results so far so want more time to assess the situation. There will be another announcement of the launch date on 12Dec09 but it will not be prior to 19Feb09. The launch has previously been delayed from 6Nov08 to 4Dec08 and then to 12Feb09.
