Extension of line 8, Mar de Cristal - Campo de las Naciones to Barajas airport and Barajas neighbourhood. A double track tunnel has been built, with a total length of 5,347 meters.
This tunnel has been constructed with two earth pressure balance machines (EPB). The machines, in their excavation, passed under an artificial lake and some building, without settements being produced.
The project also included the construction of two new stations, Barajas and Aeropuerto.