Oil tankers are slowly returning to cross the Strait of Hormuz. As shown by the animated map from MarineTraffic, ships are switching off their AIS transponders at the entrance to the strait, crossing it in “invisible mode,” and then turning AIS back on after the transit.

It’s a dangerous measure—especially in such a heavily trafficked maritime corridor—but it is being seen as the safer alternative in the face of an Iran that has repeatedly threatened to attack tankers observed transiting the strait.