...not widely reported in German media, though.
German Sailors Render Extraordinary Honors to US at Sea
Honor: The officers and crew of the FGS Niedersachsen
render honors to the USS Doyle on Sept. 11, 2003.
"Military vessels routinely render honors to military ships of other countries when they pass at sea by dipping their flag, as a sign of respect. The German frigate FGS Niedersachsen went above and beyond this normal gesture of respect when it asked to come alongside the USS Doyle on September 11, 2003, the second anniversary of the terrorist attacks on the US. ...
The unexpected gesture touched the US sailors, Vice Admiral Timothy LaFleur described in an unclassified email: “From their main mast they flew our flag and they held their covers over their hearts. Needless to say, the whole crew was choked up and a few tears formed in our eyes. Both ships stayed next to each other in silence for about 5 minutes. These are the days that remind me why I joined the Navy.”"
Update (1): Bill has some thoughts on the topic.
Update (2): It has happened before.