Valley aviation giants look to future; McDonnell Douglas will build new plant in Mesa. (McDonnell Douglas Corp. McDonnell Douglas Helicopter Co.)

McDonnell Douglas Helicopter Co. is planning to build a 75,000-square-foot metal processing facility at its headquarters complex in Mesa to support a continuing stream of work being shifted from its Culver City, Calif., plant.

Officials say no decision has been made to close the California facility, which still employs 1,200 people, and move all of its functions to Mesa, but economic conditions and continued movement into Arizona indicate that is a strong possibility.

For one thing, officials confirm that the Culver City lease will expire at the end of 1994. Should that lease not be renewed, the company has plenty of room at its sprawling Mesa campus; but permits …