Prototypes were produced even as development work was continuing—a system demanded by the use of composite materials, as the tooling required is very expensive and has to be built for production use from the outset.
Prototip tetap diproduksi bersamaan dengan pekerjaan pengembangan—sebuah sistem yang membutuhkan penggunaan material komposit, dan perlengkapannya membutuhkan biaya yang sangat mahal dan harus dibangun dari awal.