For years, Reliance Gear Corp. has manufactured gears for the aerospace industry. Located in Elmhurst, IL, Reliance has served as a Tier 2 or Tier 3 supplier. (Tier 1 suppliers work directly with the aerospace primes, the Boeings and Embraers of the world.) Like many gear shops, Reliance is certified under quality management standard ISO 9001. And its aerospace customers were satisfied with that certification. Until two years ago.