The system has unofficially achieved FOC (Full Operational Capability) but for diplomatic reasons the official announcement has been postponed
CAATSA (Countering America’s Adversaries Through Sanctions Act)
Turkey’s deepening economic woes are widely seen as one -but not the only- reason behind the delay the activation of the S-400s
Turkey’s acquisition of two Russian-supplied SAM systems remains a source of friction between the two NATO allies
Senior US official says that S-400 acquisition "challenged membership in NATO"
The US draft budget also foresees imposing sanctions on some shipping companies involved in laying pipelines being built by Russia & Turkey
The NDAA prohibits the transfer of F-35 stealth fighter jets to Turkey
Turkish President Recep Tayyip Erdoğan has made no signs that he is willing to compromise
Among the proposed sanctions packages are penalties on Turkish officials and the nation’s banking and energy sectors, as well as prohibitions on US purchases of Turkish sovereign debt
And they would do the same with the F-35 if they had been delivered...
"I will work with my colleagues to ensure there is zero chance that F-35s will leave the US for Turkey while Erdogan possesses the S-400"