Spain has selected the Airbus A321 airframe as the foundation for an “ear in the sky” capability as it restores the country’s crewed signals intelligence (SIGINT) fleet.
The Santiago II program will provide three dedicated crewed SIGINT airborne platforms to fill in the gap after Madrid retired its last Boeing 707 (designated TM.17-4 in Spanish service) and Dassault Falcon 20 (designated TM.11) electronic warfare aircraft in the 2010s.
In December 2025, the Spanish Ministry of Defence tapped Airbus and Indra to conduct an 18-month conceptual definition study for the program.
Airbus is responsible for the aircraft design and modifications, while Indra will develop the mission system, combining electronic intelligence and communications intelligence under a unified command-and-control architecture.
Once delivered, the crewed SIGINT aircraft are expected to complement Spain’s uncrewed Predator B fleet, which is being integrated with the Scalable Open Architecture Reconnaissance system from L3Harris.
Airbus A321
The Airbus A321 is a narrow-body commercial jetliner offering a relatively spacious cabin that can accommodate SIGINT crew, equipment, and mission systems.
It comes in several variants, including the A321ceo with a maximum takeoff weight (MTOW) of 93.5 tons and a range of 5,950 kilometers (3,697 miles), as well as the A321neo with an MTOW of 97 tons and an extended range of 7,400 kilometers (4,598 miles).
Madrid has not disclosed the particular configuration it has chosen for its SIGINT aircraft.
Apart from Spain, France also selected the A321 as the basis for its future “flying frigate.”
