The XB-55 project had started in 1947, but by the end of the decade it was apparent that if strategic penetration in warfare were to be successful at all, it would require aircraft much faster than the jet fighter aircraft which were then being placed into operation.
Proyek XB-55 telah dimulai pada 1947, namun pada akhir dekade itu jelas bahwa jika penetrasi strategis dalam peperangan yang sama sekali berhasil, itu akan membutuhkan pesawat jauh lebih cepat daripada pesawat tempur jet yang kemudian ditempatkan ke operasi.