Artist's impression of McDonnell Douglas cargo aircraft concept circa 1972 found on eBay. Watercolor by aircraft illustrator David Beigle
Source:
http://www.ebay.com/itm/mc-donnell-douglas-concept-illustration-for-giant-cargo-aircraft-1972/281451177145?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3De498dc4ab7c14f0d8e3d6403eb0f175d%26pid%3D100005%26prg%3D20131003132420%26rk%3D1%26rkt%3D6%26sd%3D281451171420&rt=nc
Source:
http://www.ebay.com/itm/mc-donnell-douglas-concept-illustration-for-giant-cargo-aircraft-1972/281451177145?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3De498dc4ab7c14f0d8e3d6403eb0f175d%26pid%3D100005%26prg%3D20131003132420%26rk%3D1%26rkt%3D6%26sd%3D281451171420&rt=nc