So every single flight should cut their capacity by hundred thousand pounds, because there's a <0.001% chance it need to dump fuel? Suppose we impose this rule

So every single flight should cut their capacity by hundred thousand pounds, because there's a <0.001% chance it need to dump fuel? Suppose we impose this rule. Now we will need to make up for the lost capacity by increasing the number of flights. How can that be good for the environment?