CAPE CANAVERAL Any lingering doubts about NASA's decision to ground the shuttle fleet for wiring inspections have vanished, with shuttle Endeavour -- the orbiter that had its payload removed for inspections -- turning up 20 areas of potentially hazardous wiring, including spots that were down to bare wire.

Damage to Endeavour is the most extensive found so far on any of the shuttles, according to Kennedy Space Center spokesman Bruce Buckingham.

The fleet-wide inspections were ordered after an electrical short-circuit during shuttle Columbias launch last month triggered two key main engine computers to shut down. The problem was traced to a wire that had been bent or crushed during routine preflight processing. The damaged wire then touched the head of a screw, breaking the flow of electricity and zapping the engine computers.

A second flawed wire was later found in the same, spurring officials to ground the entire fleet for thorough inspections.

"Itd be bad if we had another problem (during launch) because we didnt go and take a look," said Buckingham.

With inspections and repairs continuing, NASA is not yet ready to set launch dates for either of the remaining two missions slated to fly this year: Endeavours 11-day flight to map the Earth with radars and Discoverys planned October servicing call to the Hubble Space Telescope.

A third mission shuttle Atlantis planned December visit to the International Space Station has been bumped to Jan. 22.

Inspections on Atlantis and Columbia are complete, said Buckingham. Atlantis had one area of damage and Columbia had two. Discovery is about halfway through its inspections, with nine areas of damage found so far.

In addition to cutting out the damaged wires and splicing in new ones, workers are adding sturdy tubing to further protect bundles of wiring in high-risk areas, said Buckingham.

NASA managers plan to discuss progress on the shuttle repairs next week and possibly set target launch dates for Endeavour and Discovery.