Gamma Airlines flight #69, on which Charlie was a passenger, disappears and no trace of the plane or any wreckage is ever found even though there was an extensive search performed. Charlie's heirs sue Gamma Airlines and produce the following known facts with regard to the flight: (a) flat terrain from take-off to the intended destination and all along the planned route, (b) good flying weather at the time of the flight, and (c) all luggage was examined by electronic equipment before departure for bombs or weapons. What is the BEST argument that Charlie's heirs can make when they sue Gamma Airlines for negligence? Explain the legal theory that offers Charlie's heir the BEST chance of winning a negligence claim.