For the third time (in four tests) the U.S. Navy's Aegis air defense system intercepted a ballistic missile. The USS Lake Erie, off Hawaii, detected and attacked, with a Standard 3 anti-aircraft missile, a ballistic missile launched from the island of Kauai. The missile was intercepted while it was still ascending into the atmosphere. This is when ballistic missiles are most vulnerable. Aegis equipped destroyers or cruisers could sit off the coast of a hostile nation and look for ballistic missile launches, and knock them down. While "terminal defense" (destroying an incoming warhead) is a more popular form of anti-missile operations, it is also much more difficult. The navy approach doesn't have a lot of supporters, but there are enough to keep the development of the Aegis anti-missile software (which does most of the work) going. There are two more tests in the current development program.