During my three years on exchange with the USN many years ago, my memory tells me that their theory was that to keep one carrier operational, for each they needed four - the operational one, one working up, one working down, and one in deep maintenance or upgrade. We have two - so no surprise that we cannot keep a promise to have one doing what we said it would do. Not sure we could afford four, so perhaps we should just accept PWS failing to do what it was supposed to do.