LOS ANGELES - In March, NASA (news - web sites) launched an experimental jet that reached a record-setting speed of about 5,000 mph. Now researchers want to leave that milestone in the dust. NASA's third and last X-43A "scramjet" was set to streak over the Pacific Ocean on Monday at 7,000 mph for 10 or 11 seconds — or 10 times the speed of sound. The first X-43A flight failed in June 2001 when the booster rocket used to accelerate it to flight speed veered off course and had to be destroyed. The second flight in March was a success,...