Construction of the 4.5km line branch will serve both airport terminals will take three years to complete and includes a 3.8km tunnel beneath one of the airport's runways.

The €286m civil works contract was awarded as long ago as 2010 to construction companies Copcisa, Ferrovial and Sacyy, but the project was put on hold shortly afterwards due to budgetary constraints. Construction of the superstructure and operation of the branch will be tendered later in a separate concession contract.

This 1668mm-gauge line will presumably replace the current rail connection, which only serves Terminal 2, and is independent of the extension of Barcelona metro Line 9, which is due to reach both terminals next year.

Using the new east-west alignment, suburban trains will reach Terminal 1 from Barcelona-Sants station in just 19 minutes. The current journey time from Sants to Terminal 2 is 18 minutes via the U-shaped branch to the airport, which opened in 1975.