Here's more, with a source, for what its worth:
the second prototype of the Ju 390 actually flew from "Mont de Marsan on the Atlantic coast of France, near Bordeaux, [and] it once approached to within 20 km (12.4 miles) of New York before returning safely to base, thus validating the operational concept" (Ford, Germany's Secret Weapons, p.30).
The four-engine Me 264, initially designed in 1937 and 1938, and referred to inside the German government as the "Amerika-Bomber" or the "New York Bomber", had a range of nine thousand miles and was capable of carrying "a five-ton load of bombs to New York, a small load to the middle West, or reconnaissance missions over the West Coast and then returning to Germany without intermediate bases" (Weinberg, Germany, p.197). The Me 264 actually made its first flight in December 1942, when it flew 30 hours non-stop to New York and returned safely to Europe (Ford, Germany's Secret Weapons, p.30).