What's on the Controller's Screen

If you have ever seen a photograph or video of an air traffic control operations room, you will have noticed controllers staring intently at large, glowing screens. But what exactly are they looking at? This lesson explains what appears on a controller's radar display and how they use it to keep aircraft safe.

The Radar Display: An Overview

The radar display — often called the situation display or plan position indicator — shows a bird's-eye view (plan view) of the airspace. Imagine looking down on the world from directly above. The controller's screen shows a map-like view with the radar station at the centre (or with the display positioned to show the controller's sector of responsibility).

The display is usually shown on a high-resolution monitor with a dark background. The dark background is not just for aesthetics — it reduces eye strain during long shifts and makes the bright symbols representing aircraft easier to see.

Aircraft Symbols

Each aircraft that the radar system is tracking appears on the display as a small symbol. The exact shape of the symbol varies between different ATC systems, but common representations include:

A small dot or diamond marking the aircraft's current position
A short history trail — a series of smaller dots behind the main symbol, showing where the aircraft has been over the last few sweeps of the radar. This gives the controller an instant visual indication of the aircraft's direction and speed of movement.
A velocity vector — a line extending from the symbol in the direction of travel, showing where the aircraft will be in a set number of minutes at its current speed and heading

The Data Block

The most important element associated with each aircraft is the data block (sometimes called a track label). This is a small block of text connected to the aircraft symbol by a thin line (called a leader line). The data block contains essential information about the aircraft.

A typical data block on a UK ATC display might show:

RYR1234
350  420

This would decode as:

Element	Meaning
RYR1234	Callsign — Ryanair flight 1234
350	Current altitude — Flight Level 350 (35,000 feet)
420	Ground speed — 420 knots

More advanced systems may display additional information:

Aircraft type (e.g., B738 for a Boeing 737-800)
Destination airport (e.g., EGPK for Prestwick)
Squawk code (the four-digit transponder code)
Cleared altitude — the altitude the aircraft has been cleared to, shown alongside or instead of the current altitude if the aircraft is climbing or descending
Heading or track — the direction the aircraft is flying
An arrow or symbol indicating whether the aircraft is climbing, descending, or in level flight

Controllers can typically expand or collapse the data block to show more or less information, depending on what they need at any given moment. This helps reduce clutter during busy periods.

Sector Boundaries

The display shows the boundaries of the controller's sector — the area of airspace they are responsible for. These appear as lines on the display, often in a distinct colour. Aircraft inside the controller's sector are their responsibility; aircraft outside are someone else's.

Controllers pay special attention to aircraft approaching the sector boundary, because these will need to be handed off (transferred) to the next controller.

Airways and Waypoints

The display typically shows the airway structure — the fixed routes that aircraft follow through the airspace. These appear as lines connecting named waypoints. Waypoints may be shown as small triangles or text labels.

Knowing the airway structure helps controllers anticipate where aircraft will be heading and identify potential conflict points where routes cross.

Other Features on the Display

#### Restricted Airspace

Areas of restricted or prohibited airspace (such as military danger areas, temporary restrictions, or areas around sensitive sites) are shown on the display, often as hatched or shaded zones. Controllers must ensure that civil aircraft avoid these areas unless specifically cleared to enter.

#### Weather Overlays

Some radar displays can overlay weather information — showing areas of significant precipitation, thunderstorms, or turbulence. This helps controllers route traffic around hazardous weather. Weather data may come from the primary radar itself (which detects precipitation) or from separate weather radar systems and meteorological feeds.

#### Minimum Safe Altitude

The display may show minimum safe altitudes for different areas — the lowest altitude at which an aircraft can safely fly while maintaining clearance from terrain and obstacles. This is particularly relevant in Scotland, with its mountainous terrain.

#### Conflict Alerts

Modern ATC systems include Short-Term Conflict Alert (STCA) — an automated system that continuously analyses the radar picture and warns controllers if two aircraft are predicted to lose safe separation. When a conflict alert triggers, the affected aircraft tracks may flash or change colour, and an audible alarm may sound. This is a critical safety net that gives controllers advance warning of a developing problem.

How Controllers Read the Display

An experienced controller does not look at the display the way a passenger might look at a flight tracking website. Controllers develop a highly trained ability to:

Scan systematically: Rather than staring at one aircraft, controllers continuously scan the entire display in a disciplined pattern, checking each aircraft's position and trajectory
Spot developing situations: By looking at history trails and velocity vectors, controllers can anticipate where aircraft will be in the near future and identify potential conflicts before they develop
Prioritise: Controllers know which aircraft need attention now (those climbing, descending, or approaching sector boundaries) and which can be monitored with less urgency (those in stable, level flight)
Maintain a mental model: The display is an aid, but the controller's most important tool is their mental picture of the traffic situation. Experienced controllers can often tell you the position, altitude, and intention of every aircraft in their sector without looking at the screen.

What You Cannot See

It is worth noting what the radar display does not show:

The actual aircraft: You see a symbol, not an image of the plane. The symbol represents processed data, not a direct view.
Aircraft without transponders (on SSR-only displays): If the system relies solely on secondary radar, an aircraft with no working transponder will not appear.
Very small objects: Light aircraft, drones, and birds may not appear reliably on the radar display, depending on the radar's sensitivity and the size of the object.
Terrain detail: The display is a plan view of airspace, not a detailed topographic map. Terrain awareness is handled by separate systems.

The Prestwick Centre Display

At Prestwick Centre, controllers use the iTEC system, which provides a modern, high-resolution radar display with advanced features including automated conflict detection, electronic coordination tools, and flexible data block management. The domestic sector controllers see a real-time radar picture fed by a network of radar stations across Scotland and northern England, while the oceanic controllers see a different type of display based on procedural data and ADS-C position reports rather than radar.

Why This Matters

Understanding what controllers can see on their screens helps you appreciate the skill involved in air traffic control. A busy sector might have 20 or more aircraft on the display simultaneously, all moving, some climbing or descending, some converging, some needing to be handed off — and the controller must keep track of all of them, plan ahead, and react decisively to any developing situation. The radar display is the window through which they see the sky, and reading it accurately is a skill that takes years to master.