But repeated missile and drone strikes on Riyadh's main international airport have raised fresh questions about the limits of the kingdom's sophisticated air defenses.

Since October 6, the strikes have killed at least 20 people and injured almost 400. The deadliest attack so far happened on 10 October when 12 people were killed and more than 300 wounded.

On Monday, the kingdom vowed a "serious" response to the attacks and less than 24 hours later, Saudi strikes targeted energy facilities in Sanaa - causing massive fires and explosions that rocked the Yemeni capital.

So why have the latest Houthi attacks repeatedly penetrated Saudi defenses, and what do they reveal about the kingdom's ability to protect its most valuable assets?

Riyadh has spent billions of dollars on some of the world's most advanced air-defense systems, assembling an arsenal designed to counter precisely these threats. Its equipment includes the American-made MIM-104 Patriot, including the advanced PAC-3 variant with hit-to-kill technology, and the even more sophisticated Terminal High Altitude Area Defense (THAAD) system.

Both can intercept ballistic missiles and have demonstrated their capabilities in combat. Saudi Arabia also has a well-equipped air force, including advanced F-15s and Eurofighter Typhoons, capable of engaging drones and cruise missiles.

Yet Houthi missiles and drones have repeatedly evaded or penetrated the kingdom's defenses, exposing the difficulty of protecting a vast territory and its high-value targets from sustained attacks.

Nicholas Heras, interim executive director at the Middle East Policy Council and senior director at the New Lines Institute, said Saudi Arabia's vast territory leaves it "unusually exposed" to Houthi attacks launched from northern Yemen.

"Much of Saudi territory is desert, which makes it challenging to fully defend because of the distances that must be accounted for - and it costs more to have personnel maintain early warning systems in that terrain," Heras told Middle East Eye.

"The Houthis have a target-rich environment in Saudi Arabia that includes some of the most important oil infrastructure in the world that are more immediately exposed to the drone and missile attack capabilities that the Houthis possess."

Heras said the attacks on Riyadh were intended to send a message to Saudi Arabia amid renewed fighting in Yemen.

"The Houthis perceived a gap in Saudi capability and attention span and struck Riyadh to send a signal to Saudi Arabia that if Sanaa is hit, Riyadh will be hit," he said.