When Dr. David Dao was randomly selected to be removed from a flight, he refused and was subsequently dragged away, triggering a wave of public outrage and a flurry of apologies from United Airlines.
But how exactly was he picked? That much is less clear.
Passengers on the flight told NBC News the airline had picked passengers at random using an algorithm, but industry insiders and the airline's contract with its flyers indicate it's unlikely the algorithm left much up to chance.
Airlines overbook flights using an algorithm to offset losses from seats that would otherwise go empty should a passenger not show up.