Absolutely amazing---I believe the Mars was not only the largest flying boat ever used in regular service (US Navy) but was also the second largest (flying boat) ever built, behind the Hughes "Spruce Goose" !
Glen Martin, like Howard Hughes was a true aeronautical genious

On second thought--did, perchance, Russian A/C companies ever equal or better the Mars?

?? (the ground effect ship doesn't count)