SSSS issue
AC told me that the assignment of SSSS is entirely random. I had it on a YUL-IST-TXL run so I am convinced (like TATAL) that transiting Turkey flagged it.
(Recently, AC pulled out of IST). The other good news? It did not re-occur on my rtn. (SCL-PTY-IAD-YYZ). So perhaps it is random?
FYI, I did a couple of MRs to SIN in the past year. Its a great run, because of the aircraft (788), the lounges and the cnx.