An airport is supposed to be the one place in a capital where people are only trying to leave or arrive. On Saturday, a Houthi attack on King Khalid International Airport in Riyadh killed at least 12 of them and injured 309, according to Saudi Arabia’s General Authority of Civil Aviation (GACA). The toll is provisional, and some of the injured are in critical condition.

The dead came from across the region and beyond: four Saudis, two Bangladeshis, and one person each from the United States, Egypt, Jordan, Syria, Palestine and Sudan, as reported by Al Jazeera. Secretary of State Marco Rubio confirmed that an American was among those killed. Now President Donald Trump says he is deciding whether Washington should enter the fight.

A Week of Strikes on One Airport

Reuters reported that this was the third attack on the airport in a single week, and described it as the deadliest in the kingdom in more than a decade. That characterization is Reuters’ own. Saudi Arabia’s public alert system, the outlet noted, issued no warning before the strike.

The airport suspended operations afterward. Houthi media chief posted on X that the group had “shut down” the airport, a claim that comes from the Houthis themselves. The Saudi-led coalition separately reported that a projectile landed near King Fahd International Airport in Dammam, and said on Sunday that it intercepted a missile southeast of Riyadh, near the Prince Sultan airbase.

The coalition has not held back on language. It called the Riyadh attack a “full-fledged war crime.” Coalition spokesperson Turki al-Maliki, speaking through the Saudi Press Agency, said the strike “will be met with a firm response.” No details of that response have been given.

How Yemen Got Here

The airport attacks sit on top of a sharply worsening war inside Yemen. UN special envoy Hans Grundberg told the Security Council on Friday that the country has slid back into “full-scale war,” according to Al Jazeera’s coverage of the briefing. The UN counts at least 46 civilians killed and more than 130 injured since August.

Al Jazeera reports that the Yemeni government launched an offensive against the Houthis earlier this month, and that the Houthis answered by declaring Saudi airspace a military zone and warning airlines to stay away. The airlines listened. FlightAware data cited by CBC showed at least 124 Riyadh flights cancelled on Friday, after hundreds more the day before. Lufthansa Group has suspended its Riyadh flights through October 16, the US Embassy has urged people to avoid the airport, and Europe’s aviation safety agency, EASA, has widened its guidance on Saudi airspace.

Grundberg described the strikes as “a grave escalation.” Mohammed al-Bukhaiti, a senior Houthi official, framed them differently, telling The Week that they enforce a policy of “blockade for blockade.” The Houthis are Iran-backed, but the reporting gathered so far does not establish direct Iranian involvement in Saturday’s attack.

The Decision in Washington

For the United States, the attack lands on a question it had been avoiding. In September, Axios reported that Trump turned down a request from Crown Prince Mohammed bin Salman for US strikes on the Houthis, offering intelligence and targeting data instead. That account reached NeuralWired through secondary reporting.

His tone has changed. Trump called the attack “terrible” and “not acceptable,” said the United States “may” join the war against the Houthis, and said he “will be speaking” with the crown prince. He added that he would “move very quickly.” As of this writing, no completed call has been reported. Iran International has reported Trump saying Saudi Arabia can defend itself, which suggests his position is still moving rather than settled.

The stakes extend past Yemen. Fortune described the airport attacks as a significant escalation on the latest front of the wider Iran war, a conflict that has kept energy markets on edge since it began in late February.

What It Means for Oil

The Gulf’s role in the oil market makes any threat to Saudi infrastructure a price story. The US Energy Information Administration says Brent crude averaged around $104 a barrel in the last two weeks of the third quarter, with supply disruption out of Saudi Arabia adding pressure. Brent had fallen to $72 on July 1 before rising again after military strikes resumed on July 7.

Markets reopen Monday, and no verified Brent close for Friday or Saturday is available yet. Traders will be watching for any sign that the airport attacks are widening into a threat to Saudi energy facilities, not only its aviation.

What to Watch Next

Three things will shape the coming days. The first is the Saudi-led coalition’s promised retaliation, and whether it stays inside Yemen. The second is the outcome of Trump’s expected conversation with the crown prince, and whether “may join” becomes a decision. The third is the UN Security Council, where Saudi Arabia and Yemen’s government urged action on Friday.

Riyadh has made its position plain at the UN. Saudi envoy Abdulaziz al-Wasil said the kingdom will not allow Yemen to be a staging ground for threats to its security or shipping. A civilian airport, a provisional death toll still climbing and a US president weighing his options have put that line to its first real test.