Remember that check-in for all flights is in the Main Building, Terminal Building or T4. The Satellite Building (T4S) is only used for flights with non-Schengen destinations, wide-body aircraft and certain flights with Schengen destinations.

The two buildings are connected by the airport services tunnel (AST) and the automated people mover (APM).
Check your ticket to see the terminal where you will board. As a general rule, all Air Shuttle flights and most domestic and Schengen flights depart from T4.

Except for any last-minute changes, Schengen, domestic and Air Nostrum flights operate from T4 using boarding gates K (K86 to K93).
Non-Schengen international flights depart from the Satellite Building (T4S).
Exceptionally, the odd domestic flight (including the Air Shuttle) or Schengen flight may depart from the Satellite Building.
To find out the terminal for your flight, check the Flight arrivals and departures information.