So you’ve booked that low fare, snuggled into your window seat, and dreams of sandy beaches and charming castles are dancing in your head. All that’s left to do is half-listen to the flight attendant as she goes through the usual: 

“Put the mask on yourself first,” “Your seat cushion doubles as a flotation device…” 

You're pretty sure nothing will go wrong. The weather is gorgeous, the crew is knowledgeable, and you're ready to soar off into the friendly skies. Trouble is, on any given day, the “friendly skies” look something like this…

Image taken from www.flightradar24.com

So, just how does your pilot keep from flying straight into another metal bird going 500 miles per hour? The truth is, getting you from take-off to touch-down is a team effort that takes a ton of coordination to get just right. 

Alongside the person actually flying the plane, there’s a team of air traffic controllers (ATCs) on the ground, working like puppet-masters behind the scenes. Their main job? To keep aircraft at safe distances from each other and anything else they might collide with (aliens, Underdog, Spider-Pig…you get the picture). Sounds simple, but with so many airplanes flying overhead, how is it possible to actually maintain any order? 

While we’re at it—how do pilots and controllers even communicate when they may not speak the same language? And how many people help keep the plane safe on its course throughout the flight?  

Well, here are 7 ATC secrets that you’ll be very thankful to know the next time you fasten your seatbelt…

1. There are invisible highways in the sky 

While it might look like there are hundreds of planes flying around randomly, there’s actually a surprising amount of organization in the sky. Think about how we travel by car. We use roads to get us from A to B, and there are specific rules we all follow to get around safely. Well, when airspace was being organized, let’s just say our forebears were inspired by the way we get around on land. 

Of course, if you look up, you won’t see any actual roads and street signs in the clouds (insert Doc Brown’s wisdom here), instead, planes use designated airways (called routes) and points of reference marked by geographical coordinates (called significant points). 

Unfortunately for the air traffic controllers who have to memorize them all, these airways don’t have catchy and simple names like “Birch Road” or “Maple Street”. Instead, they are usually  named a letter followed by one to three numbers. So you might have, the P732 (Papa-seven-tree-two) or the W59 (Whiskey-fife-niner). 

The significant point naming rules are simple. As long as the name has five characters, is unique and is easy to pronounce, it’s fair game. Most of the time the names are just random, pronounceable combinations of letters (think OMSUK, north of Cancun, or ZADON over Seattle). But with all that freedom, they’re also fair game for paying homage to local celebrities or other cultural icons. Three guesses which Florida airport has HKUNA (Hakuna), MTATA (Matata) and RFIKI (Rafiki) on its arrival route. 

Put the routes and significant points together, and it becomes way easier for pilots and ATCs to talk about where the plane is heading.

2. There’s one critical document that pilots must send ATCs before each flight 

Before entering any airspace where ATC service is provided, pilots or their airline must file what’s called a ‘flight plan’. This plan is shared with all the air traffic control units that the plane will be in contact with throughout the flight. Flight plans give controllers some key information in advance, like: 

• Which route the plane is planning on taking and the significant points it will cross 
• Which airport the plane will depart from and where it intends to land
• The emergency equipment the aircraft has on board (in the unlikely case of an emergency, ATC might have to give this information to a search and rescue team) 
• The alternate airport where the pilot would like to land if something goes wrong (more on that in a bit)
• And the altitude or flight level the pilot is requesting to fly 

Basically, it tells controllers everything they need to know to be able to track the plane’s journey safely and efficiently.

But these’s still one big (and, dare we say, blinding) question… How do ATCs actually control anything when the planes are out of sight?

CC image courtesy of EUROCONTROL.INT on Flickr

For most ATC centers, that’s where radar comes in. Controllers can see the position of each aircraft on radar screens long after the plane has left the airport. Plus, with flight plan information linked to each specific flight, ATCs can even pull up a visual of the future route progression of each airplane. This info tells them when two aircraft might be on a collision course, so they can calmly give pilots control instructions to avoid disaster long before a problem ever develops.

3. Cardinal direction matters for more than just pointing the aircraft the right way

That’s right, whether your plane is pointing east or west actually determines the altitude it will fly at. 

Aircraft flying towards the east (0 – 179 degrees) fly at “odd” levels (like 31,000ft, 33,000ft and so on) and those flying towards the west (180 – 359 degrees)  fly at “even” levels (32,000ft, 34,000ft…you get the idea). 

Controllers and pilots refer to these as flight levels, where 30,000ft would be flight level 300 (FL300) and 41,000ft would be flight level 410 (FL410). 

It’s easy to see why these conventions are in place. If two aircraft flying the same route in opposite directions approach each other at the same flight level, that could easily end in a game over scenario. Instead, this system arranges  air traffic so that planes can fly in opposite directions on the same route, while always staying vertically separated from each other. 

4. There’s a special controller for each phase of flight

Yep, your pilot isn’t just talking to one person on the ground! Instead, there are 3 main types of air traffic controllers, all playing a high stakes game of hot potato with your flight.

Aerodrome controllers work from an ATC tower at the airport. They provide control service to air traffic at and in the vicinity of the aerodrome. 

This includes giving landing and take-off clearances to aircraft, plus helping them get to and from their gates safely.  Once your plane is off the ground, the aerodrome controller hands you off to Approach/Departure.

CC image courtesy of Jon Rapp on Flickr

Approach controllers sequence aircraft for landing at, and departing from, airports. 

It’s one thing when planes are flying on their courses in the open sky, but around an airport, planes are concentrated in a small area. These controllers make sure planes approach or depart from the vicinity of the airport without any incidents.

Once your aircraft leaves the approach controller’s area of jurisdiction, it’s handed over to the Area controller. 

Area controllers (also called en-route controllers) are responsible for aircraft for the longest portion of their flight. 

These controllers work from air traffic control centers. Unlike the tower (which has to be at the airport, so the aerodrome controller can look out and see the planes, runways, and taxiways), an ATC center may not be anywhere near an airport. For example, the Los Angeles Air Route Traffic Control Center is about 72 miles from LAX. Area controllers direct  air traffic using radar screens. 

While there are lots of regulations in aviation that help to create an orderly arrangement, the system isn’t perfect on its own. With so many planes in the sky, and so many crisscrossing routes, ATCs play a crucial role in preventing aircraft collisions. They give pilots the instructions and information necessary to keep everybody in their airspace safe. 

5. There are way more ATCs looking after your plane than you think 

So, you know there are three different types of controllers, but that doesn’t really tell us how many individual controllers your plane comes into contact with. Here’s a typical example: 

A flight from Miami, USA to Barranquilla, Colombia, only takes around 2 hours and 45 minutes. But, in that time, it passes through four different  flight information regions (FIRs). Airspace all over the globe is divided into these regions of varying shapes and sizes, and each is controlled by a single authority (usually a country or a state within a country). For each FIR, a new area controller takes charge of your plane: first, in Miami; then Havana, Cuba; then Kingston, Jamaica; and finally, Barranquilla, Colombia.

Add to that the aerodrome and approach controllers at both your departure and arrival airports, and that’s at least eight different controllers taking care of your plane on that one trip!

6. Everybody speaks the same language, and it might not be the one you think

ATCs and pilots are about as international as they come. After all, aviation does connect the world more than any other form of travel. You might have a  German pilot pass through the airspace of French ATCs, while flying the same routes as a pilot from India. 

To overcome the language barrier, English is the de facto universal language of the skies. 

While one language makes communication possible, different accents or interference might still cause plenty of confusion in radio transmissions. It’s also really important to be able to convey a message quickly and accurately without rambling through a whole speech in someone’s second language.

For these reasons, ATCs and pilots communicate with special phraseology, or a language made just for them. Remember the Papa-seven-tree-two (P732) and the Whiskey-fife-niner (W59) from the highways in the sky earlier? Those weren’t typos. Even the numbers are said and pronounced in specific ways to make sure they’re as clear as possible in radio transmissions. 

Other examples include words and phrases like:

— Break, break:  Indicates separation between messages transmitted to different aircraft in a very busy environment.

— How do you read?: How clear is my transmission?

— Acknowledge: Let me know that you have received and understood this message.

— Wilco: I understand your last message and will comply with it. 

— Correct: True and accurate

— Affirm: Yes

Having specific phrases like this allows for clear communication in as few words as possible. Some words, like the response, “correct”, also prevent ambiguity.

In general usage, we might confirm that something is true by saying “right”. But imagine if a pilot heard “right” over a spotty radio transmission. They might interpret it as an instruction to turn to the right—and maybe turning right at that moment could be the worst possible move for the pilot to make. Phraseology takes care of that problem, and makes communication in the skies clearer.

7. A few minutes’ delay might prevent disaster

Despite all the carefully set out regulations, and vigilance on the part of controllers and pilots, aviation isn’t  always smooth sailing (or, should we say smooth flying?)

If there’s bad weather, a lot of  traffic at an airport, an unexpected runway closure or any number of other reasons, your flight might not be able to land as planned.

In these situations, controllers have to make a decision about where to send your plane, and in extreme cases, your aircraft might have to fly instead to that alternate airport mentioned above. 

But if you’ve ever been one of those unlucky souls eyeing your dream vacation out the window  while your plane just kept going around and around in circles instead of landing, then you’ve likely been in a holding pattern – not ideal when you only have four hours before your best friend from high school’s sister’s wedding!

Holding means exactly that – you’re going to fly around a specific location (called a holding fix), while you wait for whatever’s keeping you up there to change or improve. 

If the controller determines that the situation might soon clear up, holding is actually a blessing in disguise. The alternatives are: clear you to land when it’s not actually safe (nobody wants that), or send your plane to another airport where you’ll undoubtedly lose more time. At that point, you’ll surely miss Janice’s sister, Christina’s wedding, although you’re still not sure how you even got invited. 

CC image courtesy of Joan Lopez i Casanoves on Flickr

With over 100,000 aircraft taking to the skies every day, it’s no accident that flying is still the safest way to travel. The next time you fly home for the holidays, or jet off on vacation, definitely pay attention to those pre-flight safety instructions! But also remember that your journey is being guided by those men and women on the ground who work 24 hours a day, 365 days a year to make sure you stay safe from take off to touch down.