Right, but it sound like the aerodynamics have been deteriorating model-by-model, as they move away from the original design. This creeping change must be real

Right, but it sound like the aerodynamics have been deteriorating model-by-model, as they move away from the original design. This creeping change must be really hard to regulate right. A terrible new design you could refuse to certify, but a terrible one which is only a few percent worse than the one your predecessor certified a decade ago... it would take a lot of confidence to say no.