The US government approved a Kuwaiti order for $2 billion in counter-drone systems, days after an Iranian strike got through the country’s defenses and hit Kuwait International Airport, killing one person and injuring 63.

Kuwait already has Patriot missile batteries and other lines of defense, but its capital city sits less than 90 kilometers from Iran, so defenders can have as little as 45 seconds to spot a weapon and try to intercept it before it reaches its target, The National reported. Patriots are built to stop ballistic missiles, but drones are harder to deal with as they fly low and can come from unexpected directions; the more an attacker launches at once, the more likely it is that one slips through. Analysts say the big challenge is linking radars, sensors, and command systems tightly enough so that they can react in time.