It is possible that Boeing and BAE have a totally different ethos on the contracts?
With Boeing they come up with a technical proposal to produce a system to meet the SOR. If a change is then required they will provide a cost estimate of such size that there is really no prospect for deviating from the original Spec. This means that their product can be produced in a standard form in a fairly short time scale.
BAE, OTOH, with no production line to start with will agree to any change in the SOR almost to keep the customer sweet and the money rolling in. The result? A rolling goat.
Is that about right?
Would it have been better to award an aircraft contract to BAE and a systems contract to a different contractor?