There has been quite a lot of comment here and analysis elsewhere, albeit some months ago, regarding the use of non-naval ships in incidents in this maritime area. IIRC IISS published an Adelphi Paper on the growth in para-military / non-naval / law enforcement vessels in the Pacific; sometimes with very odd aspects, like US Coast Guard ships carrying Chinese law enforcement staff in the Bering Street area.

So this latest incident with Chinese maritime surveillance ships comes as no surprise.

One of the big issue in the South China Sea is the lack of information on whose ships are where and what are they doing.

Vietnam's maritime safety bureau or whatever it is called has several very modern, state of the art, Swedish built maritime surveillance aircraft and is one of the few countries that has the capability to gather and process the information. Incidentally the USCG has a few of them too.

I am 95% certain the aircraft sold isthe Saab 2000 MPA:http://www.saabgroup.com/Air/Airborn...Saab_2000_MPA/