When I started this book, I admit that I hoped what would happen is that someone would get killed and then Poirot would somehow solve the mystery before the plane ever touched ground. It would be like Murder on the Orient Express except … on an airplane. Which was just two Poirot books ago, which is probably one of the reasons Christie didn’t do that. (For an author so prolific, I find her wonderfully creative from book to book in her contexts and twists and even the flow of action.)
Instead, the murder takes place on an airplane in plain view of everyone, which narrows quite a bit both the field of potential murderers (tough to have someone stowed away on a plane) and the method. Poirot works through, candidate by candidate, until he reaches a wholly surprising conclusion.
I found it engaging, interesting, and the ending was satisfying.