A US Navy helicopter just vanished near Yemen's blockaded coast

This helicopter is a Navy workhorse.

It flies off ships and shore bases. It hunts submarines and surface ships, does electronic warfare, and runs command and control. It's exactly the aircraft the US Navy keeps near a stretch of water it's watching closely.

And right now, the Red Sea is that stretch of water.

A month ago, Houthi forces took the port city of Mocha, on Yemen's southern coast. Within days they'd taken the rest of Yemen's Red Sea coastline too — Mayun Island in the Bab al-Mandeb Strait, and the Hanish Islands. Before that, in July, the Houthis had already declared a naval blockade of Saudi Arabia and threatened ships using Saudi ports.

Saudi Arabia hit back. Its forces struck Mocha's airport after the Houthis took it. No damage or deaths were reported at the time.

Saudi Arabia now relies more on this Red Sea route for its oil exports too, because shipping through the Strait of Hormuz, further east, has been disrupted separately.

So here's where this sits. A US military helicopter has gone dark, at low altitude, on a coastline where an armed group has just taken territory and declared a blockade.

That doesn't mean it was an attack. The US Navy hasn't said that. The Houthis haven't said anything. Nobody has confirmed any hostile action at all.

It could just be mechanical. Helicopters declare emergencies for engine trouble, instrument failure, all sorts of reasons that have nothing to do with anyone attacking them.

But the location is why people are watching this closely. Yanbu sits on the same coastline the Houthis have been fighting over for weeks.

So there are three questions right now. What caused the emergency. Whether the helicopter went down or landed safely. And whether the crew is safe.

Nobody outside the US Navy can answer any of them. And the Navy isn't saying anything yet.