The number of near midair collisions and errors by air traffic controllers dropped significantly during the first half of the year, the Federal Aviation Administration reported Monday.

Near misses fell by 27 percent to 366 incidents from January to June compared with 500 incidents during the same period in 1987.A near miss occurs when two or more aircraft come within 500 feet of each other or when a pilot believes the potential for a collision exists.

The FAA also reported the number of errors by air traffic controllers dropped 18 percent to 518 compared with 635 during the first half of last year.