On December 30, 2006, a powerful car bomb detonated at Madrid–Barajas Airport, specifically targeting the vicinity of Terminal 4. The explosion occurred in the early morning hours, resulting in the deaths of two Ecuadorian nationals who were traveling to Spain for work. The shocking attack was orchestrated by the Basque separatist group ETA, renowned for its violent campaign advocating for independence from Spain. The timing and location of the bombing underscored the unpredictability and severity of ETA's operations against the backdrop of increasingly strained political landscapes in Spain.

In the months leading up to the bombing, peace negotiations between ETA and the Spanish government were attempted, but these efforts began to falter, leading to escalating violence. The attack not only inflicted physical harm but also instilled fear among citizens and travelers at one of Europe’s busiest transport hubs. The Spanish government condemned the attack, accusing ETA of undermining peace processes and expressing outrage at the loss of innocent lives.

The bombing prompted immediate security overhauls at airports and other public transportation hubs across Spain. Moreover, it ignited debates surrounding national security policies, counter-terrorism strategies, and the government's approach toward separatist movements. Strong public sentiment rallied against ETA, calling for unity against terrorism, thus reinforcing the government's resolve to combat the group.