Raytheon Technologies, a unit of RTX Corp, won a $1.7 billion contract to deliver four Patriot air and missile defense systems to Spain, the US defense contractor said on Tuesday.

Patriot, short for ‘phased array tracking radar for target interception’, is a mobile surface-to-air missile system. It detects, tracks and destroys incoming aircraft and missiles.

Developed by Raytheon, the system is the US Army’s main air and missile defense system, deployed worldwide to counter aircraft and missile threats in regions including the Middle East, South Korea and Guam.

Raytheon has partnered with Spanish defense companies, including Sener, to supply components such as the electro-mechanical control system for the GEM-T missile under its global Patriot supply chain.

Patriot batteries are highly effective against missiles and aircraft, but using them to shoot down cheap drones is an expensive proposition.

A newly manufactured single Patriot battery costs more than $1 billion, including $400 million for the system and $690 million for the missiles in the battery, according to the ⁠Center for Strategic and International Studies.

Patriot interceptors are estimated to cost about $4 million per missile.

The deal comes as Germany, the Netherlands and Romania placed orders for additional Patriot systems this year.

Separately, the US State Department in November approved a potential $105 million sale of equipment to sustain Ukraine’s Patriot air defense systems.