A cavernous, 43-year-old wind tunnel used for aircraft flight testing at NASA's Ames Research Center near Mountain View was reopened after a seven-year program of modernization that boosted air speeds as much as 50%. Visitors were invited to watch a demonstration in which 30-foot fans generated winds up to 345 m.p.h. through the National Full-Scale Aerodynamics Complex, capable of containing a full-size conventional fighter jet or a Lear jet, and said to be the largest facility of its kind in the world. "It's sort of a small hurricane," said Peter W. Waller, spokesman for NASA at Moffett Field, 30 miles south of San Francisco. "This is real progress in aeronautics that will enable us to have better flight testing of the nation's aircrafts, and thus safer planes."