If there is one thing US authorities have been absolutely clear on their communications with shipping, it is their desire for vessels to have their AIS turned on just about all the time.

Two advisories from the country's Office of Foreign Assets Control (Ofac) in March 2019 warned companies that ships up to no good might disable the tracking system to hide their behaviour.

In May, Ofac joined the US Coast Guard and the State Department to publish more tailored guidance, instructing everyone from shipowners and crews to flag states to keep AIS on, lest they attract suspicion for sanctions non-compliance.