In 1969, a DC-9 Series 20 at Long Beach was fitted with an Elliott Flight Automation Head-up display by McDonnell Douglas and used for successful three-month-long trials with pilots from various airlines, the Federal Aviation Administration, and the US Air Force [REF].
The Series 20 was originally certificated at an MTOW of but this was increased to , some 8 percent up on the higher weight Series 14s and 15s.