I traveled with my preschooler to Europe without DH. Went fine, apart from the red-eye flight.
He had fallen asleep in my arms. At some point during the night, I woke up to feel sticky stuff everywhere on my hands and arms, and his face and front. Using the overhead light, I saw he had had a massive nosebleed. I couldn't clean it by myself, the call button didn't produce a flight attendant, so I made my way down the aisle in the dark. The attendants were chatting quietly in the well-lit back room. They saw a woman lurching in from the dark corridor cradling a small child literally covered in blood. You couldn't see his face at all, and his shirt was soaked. It was like a scene from a movie.
After recovering from the shock, they were very helpful