The U.S. space agency says repairs to the space shuttle Endeavour are taking longer than expected, meaning the agency's farewell mission may have to be postponed again.
NASA said Wednesday the earliest Endeavour could be launched was on May 10, but it could be later.
The space agency said they have replaced a faulty switch box that controls power to heaters that keep the shuttle's fuel lines from freezing. Engineers will continue testing to determine what caused the system to fail to see if other parts will have to be replaced.
This will be Endeavour's last flight before the shuttle is retired and sent to a Los Angeles science museum for display.
Astronaut Mark Kelly is commanding Endeavour and its six-person crew. Kelly's wife, Congresswoman Gabrielle Giffords, who was shot and gravely wounded in a January assassination attempt, was in Florida to witness Friday's launch. Her spokesman says she has returned to a Houston rehabilitation center and will go back to Florida for the rescheduled launch.
Endeavour is to deliver a $2 billion scientific instrument called an Alpha Magnetic Spectrometer to the International Space Station. The instrument is designed to search for cosmic rays throughout the universe. After Endeavour, there will be just one more space shuttle flight before NASA ends the 30-year old program.