Trump weighs joining Saudi strikes on the Houthis after a missile kills 12 at Riyadh's airport

Hours after the strike, the Saudi energy ministry was still promoting an international energy conference set to open in Riyadh on Sunday ^[12]. The airport was closed through midnight and flights were diverted ^[6], while the US, Britain, Germany, Australia and Canada told their citizens to avoid it ^[20]. The AP report carried by Fortune says the attacks on the world's top oil exporter have rattled markets ^[11]. It does not give prices.

Earlier strikes on the same airport during the past week killed four people ^[5], so Saturday's 12 deaths take the week's toll there to 16 ^[22]. A missile hit the complex that houses domestic terminals 3 and 4, a regional official told the AP on condition of anonymity ^[9]. The same day the Saudi-led coalition reported a projectile falling near King Fahd International Airport in Dammam and a Houthi ballistic missile intercepted in Al-Kharj governorate, southeast of Riyadh ^[21].

Interceptions cost missiles, and the kingdom is short of them. Regional officials told the AP last month that Saudi Arabia is running low on interceptors and has asked France, Britain, Pakistan and Egypt for air defense support ^[16]. One noted that the US has seen its own stock dwindle during the war with Iran ^[16]. We think the dwindling US stock explains why the request went to four other capitals. US help so far has been intelligence sharing, target identification and planning for the offensive ^[17], and the AP expects the airport deaths to raise Saudi pressure on allies for military support ^[19].

Trump left the door open on Saturday. "We may. We're going to look at it," Trump said. "We just found out about the recent attack. So we'll make a decision. We move very quickly." ^[8] Strikes on launch sites would be the offensive answer to a defensive shortage, in our view.

The paths diverge from here. US aircraft could join the coalition's air campaign ^[8]. Oman, which sits across the Strait of Hormuz from Iran and has mediated at times, is the other channel: Saudi Arabia said its foreign minister and his Omani counterpart discussed "supporting diplomatic solutions to de-escalate tensions" ^[18]. Or the Houthis could widen their targets. They told the AP they hit only Saudi shipping, as part of a blockade answering one imposed on them ^[14].

The only price in the material is a narrow one. A prediction market cited by Crypto Briefing put the chance of Houthi forces entering Aden at 7% by October 31 and 26% by December 31 ^[4]. If the two contracts are consistent, about 19 percentage points of that probability falls in November and December ^[23]. Traders rate a quick ground breakthrough as unlikely and a year-end one at roughly one in four ^[4].

We think the risk to Gulf energy and transport routes rose this week, and Trump's choice decides whether the US becomes a party to it. The view is wrong if the Houthis keep to Saudi targets while the Oman channel produces talks. In that case the strikes remain a Saudi air-defense problem, with the kingdom drawing on interceptor stocks officials already describe as low ^[16].