Recently, I started to detect many P8 Poseidon aircraft above South China Sea, like if a dozen of different P8 were flying in the area each day. The only explanation I see is that they are doing ADS-B code hopping, switching to a new TACTICAL code every few minutes.
Here are some of the codes I detected in the past few days: AE686A, AE6879, AE6889, AE67B3, AE6784, AE687D, AE6850, AE6854, AE6809, AE6793, AE6807, AE6845, AE6819, AE6836, AE67C2, AE67DC, AE6885, AE67D6, AE6813, AE687E, AE689E, AE6884, AE67DE, AE6803, AE682D, AE687C, AE6849, AE68A2.
Few more codes detected recently: AE6848, AE67DF, AE6870, AE6883, AE683D, AE6822, AE6814
There are a lot of US military activity in the area between Taiwan, Hong Kong and the South China Sea. Transports, SIGINT, reconnaissance, protection of US carriers in the area… mainly conducted by the US Air Force and the US Navy. Here is a list of planes seen in past few months (click on the link to see the radar map when the trackers got a MLAT position – these aircraft generally do not broadcast their position on ADSB):
AE049B – Tail number: 61-0313 – Boeing KC-135R – US Air Force
AE1492 – Tail number: 96-0042 – Boeing E-8C Joint Stars – US Air Force