In the early seventies, I had taken my sister to LAX to fly back to Cleveland. In those days, one could go along to the gate with a departing passenger, and so I did. My sister was flying on a United 474 to Chicago and then changing to a 727 to Cleveland. When it was time to board, my sister and I said our goodbyes, hugged and kissed and off she boarded. I've always loved trains, planes, cars and ships and wanted to watch the big SOB push back. When I looked out the window, I did a double take. There were three engines on the visible right wing. I wondered to myself, since when did Boeing start building six engined 747s?
When the big airplane was turned around to taxi, I did a second double take. The starboard wing only had two engines mounted on it. Now I was completely dumbfounded, so I asked the agent at the gate what was going on. He explained to me that when United needed to have major work done on an engine, the engine was sent to their Chicago maintenance facility and the only practical way to transport these huge engines was to simply attach it to the wing of a 747 and let it rack up a few Frequent-Flier miles.
I have flown a lot over the last forty years. On 747s and L1011s all over the USA and to Japan and Europe. On VC-10s to Austrailia, DC-10s to Korea, on 727s, 737s, 757s and 767s. I've been on hundreds of flights. Hell I even flew a bunch myself as a licensed pilot, but I never saw an odd number of engines on an airplane again. I started wondering if maybe I didn't dream it. It seemed so bizarre, but thanks to Google I found a few of these images to put my feeble mind at ease.