The 717 is actually not an original Boeing or McDonnell Douglas design; it&#x27;s a refinement of a very old DC-9 airframe from the 60s massively upgraded with modern avionics and modern systems. The DC-9s (and later, the MD-80&#x2F;90s) were very well-engineered aircraft, and the fact that their core airframe designs are still in operation some five decades later is a testament to how sound Douglas&#x27; original engineering and design methodology was.