What to know

• Trump said the US may join Saudi-led strikes against Yemen’s Houthis after a missile hit Riyadh’s King Khalid International Airport, injuring several people and escalating regional tensions. No final decision has been announced.S1
• Saudi Arabia vowed to retaliate against Yemen’s Houthi rebels on Sunday after a strike on Riyadh’s international airport killed a dozen people and wounded more than 300, marking the kingdom's deadliest strike in a decade. Follow our liveblog for the latest dev...S2