Airports are a non-place, a transit area that travelers -and their companions who go to see them off or greet them- pass through every day on their way to or from their destination. But at Adolfo Suárez-Madrid Barajas Airport there is also a place that is not a transit area and that is more designed to be there -if only for a while-: the Spotters Zone, a totally free aircraft viewpoint.
To access it, you don’t need a boarding pass, just present your valid ID card at the accreditation booth, before the security checkpoint. There, the interested person will be identified and will be given a card -only one per person- which will be used to enter and exit the viewpoint.
Once obtained, the security personnel will accompany and open the access door for those who have registered both at the entrance and exit. And be careful: the card must be returned at the end of the tour.
Airplane observation deck rules and recommendations

As for the prohibitions, Aena points out that the following are not allowed: the use of spotlights, lasers or any other element that may dazzle airport staff; crossing the limits of the designated area; throwing objects, papers or waste on the ground; smoking; climbing on the benches; accessing with pets or accessing with children under 16 if they are unaccompanied.
Among the recommendations is the importance of watching your belongings at all times (and if it is windy, pay special attention to objects that may fly away), as well as picking up the garbage generated during the time you are there.
Picnicking is allowed -in fact, in this video by @thewotme you can see the tables set up to have a snack while watching the hustle and bustle on the track-, but the only food you can bring in are sandwiches. Alcoholic beverages are also not allowed.
Opening hours and how to get to the aircraft observation deck
The viewpoint is open all day, from 7:30 am to 9:30 pm, and is located on the Iberia ring road, next to the central access security checkpoint.
If you come by car you can enter the following coordinates in your GPS: 40°28’52.6 “N 3°34’43.2 “W.
The trick of the colored columns at T4

Besides this viewpoint, there are other hacks that not everyone knows about Madrid Airport. Perhaps one of the most surprising – and useful – when it comes to orientation is the color system of the columns in T4: they change color to adopt the color of the nearest boarding gate, so that at a glance (and even at a distance) you can know where to go to catch your flight.