Well, in a mass balance equation, if there's more emitted than exists in the system at its initial conditions, there must be a mass inflow unaccounted for somethere.

Clearly, the missing figure must be the carbon in the CO2 that is admitted into the aircraft (i.e. through the engine intakes) before it is "emitted" with the other gases. But CO2 is only present in air at 0.03%, so even on the cited flight to Japan it's hard to imagine that this would allow the plane to land without at least a few missing bodies.

Or what about diamonds? Diamonds are made of carbon, right? Maybe it's the diamonds we're not properly accounting for.