@LedSled came close, others noted that these events are most often weather related. WFT guys? If the weather at your departure point is so bad that you cannot return, whether on one engine or two, perhaps a better answer is to keep the SOB on the ground. Regardless of aircraft type, a cute little yellow Piper or the monster A380, if you don't like the weather, Do Not Fly! IIRC, that subject was addressed during Day ONE of my ground training many decades ago.
