Oh cool, so I can fly commercial all I want at zero marginal CO2 emissions just because they don't have to build an extra plane just for me? I can burn that jet fuel and not feel bad because they were going to burn that gallon of fuel anyway?
Some of these arguments are so silly that I'm starting to understand why the EU thinks regulations are a free lunch to improve the environment with no costs whatsoever.
The analogy doesn't hold.
Airlines adjust capacity to demand — empty seats represent foregone revenue and future flights get cancelled or downsized.
Cargo ships don't work that way. A container ship returns to Asia whether it's carrying 1000 containers or 5000. The marginal emissions of an additional backload container are genuinely close to zero, not as a rhetorical trick but as a structural feature of how bulk shipping economics work.