What is the US Flotilla Route?
Recently a US Navy LCS went through the area...maybe that is what it is talking about. The US Navy made the following statement about that transit:
"As part of our strategic rebalance to bring our newest and most capable Navy platforms to the Indo-Asia-Pacific, a regular presence in Southeast Asia. Routine operations like the one USS Fort Worth just completed in the South China Sea will be the new normal as we welcome four LCSs to the region in the coming years," Capt. Fred Kacher, commodore of the Navy's Destroyer Squadron 7, said in the Navy release.
So my guess is that the "US Flotilla Route" shown here is the route that ship took and what some might expect to be the route used by future vessels...though I imagine the route will vary and never be predictable.