Stock Photo - 03/21/2000 __ Underneath the 26.3_foot vertical tail structure of Space Shuttle Atlantis, a worker in the Vehicle Assembly Building maneuvers equipment under Main Engine No. 1 in order to remove it. An inventory review concerning defective main engine fuel pump tip seals indicated that defective seals may be present on the fuel pump for the engine. The decision was made to replace the suspect engine with one originally slated for Discovery. The main engine nozzles, visible in the photo, are 7.8 feet across and 9.4 feet high. Space Shuttle Atlantis is scheduled to launch no earlier than April 17, 2000, on mission STS_101 to resupply the International Space Station for the arrival of the next pressurized module, the Russian_built Zvezda