In 2002 the enlargement works of Madrid's Barajas airport began, the new T-4 terminal and two new runways. Said infrastructures were affected by the fact that a part of the 400 kV line (double circuit San Sebastián de los Reyes-Loeches-Morata) ran very close to the new runways under constructed. AENA, the airports authority, asked Red Eléctrica for a solution to this problem, and it was decided to bury a 12.7 km section of this line, which is very important in supplying the capital's distribution substations.