Complex, he said, was like a jet plane -- certainly a challenge to put together if taken apart, but not impossible to reassemble, especially given good diagrams and an expert jet assembly team.
Complicated, on the other hand, was more like a bowl of spaghetti. If you drew out one strand with your fork, you had forever changed the bowl's contents. You could not recreate this, even trying to return the strand to its original place.
Flying, I think, is more complex than complicated. Overwhelming to the new student pilot, with time, the pieces fit together like a 1000-piece puzzle, and with the right instructor and a ready body and willing mind, learning to fly can be accomplished.