If I want to be a commercial flight engineer, would it be best for me to join the USAF as a flight engineer to start my career?

The position of Flight Engineer has been phased out over the last twenty or so years as aircraft manufacturers have designed the cockpits to operate with a two person crew. Even aircraft initially certified with a three person crew have been modified and updated with the technology to now require only two person flight crews.

The position of Flight Engineer is now a dead career path. I suggest you consider a different path in the aviation world and there are many to choose from.

The Boeing Comapny TBC made the first switch from traditional 3 man flight decks with flight engineer having a side facing panel, to 2 man cockpit when it designed the flight deck for B747-400 series and MD-11 acquired from McDonnel Douglas after merger.
The new flight deck was designed to have all the major aircaft systems sending serviceability information into one central computer which monitored the status of the systems on continuous basis and illuminated warning lights on the central warning panel.
We have to understand that each of these aircrafts have several systems and monitoring them separately was job of flight engineer along with calculations of performance data for take off and landing and preflight checks and many other duties.

It is true that all the modern twin and multi engine commercial jets being manufactured by Boeing and Airbus Industires have adopted the two man front facing flight deck, with no side facing panel. The old classic B747s nearly 800 or 900 of them are getting grounded fast because of scarcity of the old spare parts and non efficient fuel engines and higher noise levels and operation restrictions imposed on them in Europe.
USAF still operates KC-10 the inflight fuel tankers and C-130 with flight engineers mandated for their operations.

So the professional career of Flight Engineers ihas no future in commercial and even in airforce but as the old generation of aircrafts get grounded with their age, the remaining Flight Enginees will keep retiring like what happened to the professional Navigators.

Hi Henry;
The Flight Engineer job has gone away on commerical airlines for the last 10 years or so. The new airliners now in service are flown by a flight crew of 2 pilots. A Captain and a First Officer. The aircraft manufacturers now have made the aircraft systems easier to manage and are great to fly after the early narrow body jets.
The only aircraft that still require a Flight Engineer are still flown by the military. The USAF uses a F/E on the old Boeing 707 (KC-135 or RC-135). The Cargo aircraft still using a F/E are the Lockheed C-141 and C-5. The Lockheed C-130 are built now for a flight crew of 2.....pilot and co-pilot.

Flight engineers have become a thing of the past in our modern world of aviation. New generation aircraft do not require flight engineers because the have been replaced by computers. Their are still a few aircraft such as the B-727 and older model B-747's that require engineers but most have been replaced by more fuel efficient and friendlier to the environment aircraft. The USAF and the Navy still fly some older model aircraft that require flight engineers such as the KC-135, C-130 and some helicopters. The demand for qualified pilots in civil aviation has grown at great paces and airlines are having a hard time filling these positions. Maybe that is a career goal you might want to pursue.