Highways in the Skies

Mapping Plane Routes

By Michel Treskin
Editor Jennifer J. Lcelle
September 10, 2021

Have you ever wondered how airplanes navigate around the world? It’s not like everyone can go wherever they want as it’s not a free for all. There are set air corridors, or navigation tracks, that must be followed when flying in controlled airspace.

There are two main sets of rules when you fly:

  1. Either you maintain visual meteorological conditions (VMC — clear of clouds); or,
  2. You fly under instrument conditions (IMC).

Most general aviation — privately owned and small planes — tend to fly visually, which is below 10,000 feet.

Airliners, private jets, large turboprops will always fly under instrument rules. Because clouds are mostly present at medium and high altitudes you need to be on flight instruments (Primary Flight Instruments – PFD) to fly through them.

Not to mention the thousands of airplanes flying at the same time crisscrossing the same airspace as others, making air traffic controllers (ATC) the policemen of the airways.

Flying Low or High

If flying visually, always stay clear of clouds, have the ground visual and keep an eye out for other airplanes. If you are flying on a westerly heading, your altitude must be even numbers plus 500 feet. In other words, it should be 4,500, 6,500, etc.

However, if flying on an easterly heading, your altitude should be odd numbers plus 500 feet such as 5500, 7500, 9500. You can see there is already some order at lower altitudes.

If you decide to fly under instrument conditions, you cannot maintain visual, the rules are the same as VFR but minus 500 feet. When flying in instrument conditions, you must be under air traffic control radar. They are your eyes and keep other airplanes clear of your airspace.

Airliners will always fly high because of fuel savings and avoiding bad weather. The higher they can go, the less fuel the engines will consume. Airliners will always operate under instrument flight rules (IFR) because that is where everyone goes — as high as possible.

Airliners and other performance aircrafts such as military jets and business jets are also trying to fly as high as they can. Ground controllers all over the world are in charge of those airplanes. They provide traffic information to all and they maintain order on the airways.

These airways or flight corridors are everywhere. Each airliner will file a flight plan before taking off. This plan will provide flight details for the ground controllers and include altitudes, the airways they will fly, the equipment they have, the fuel on board and their endurance. It will also have diversion airfields in case the weather is worse at destination

Once the flight plan has been accepted and entered in the worldwide air navigation system, the flight is released and the aircraft is given permission to start its journey. As the aircraft progresses to its destination, every route segment is monitored, and communication is always maintained between pilot and controller.

The vertical separation is 1,000 feet if the flight is operating above 29,000 feet. This is why, as a passenger, you might see another aircraft below or above your plane. From the ground, you will see the condensation trails (contrails) made by the engine exhaust which looks like white ribbons.

There will be many crisscrossing each other in the sky. Some will be on the same route but flying either lower or higher. Eventually, these contrails disappears as they dry up.

Getting Higher

Some airplanes can fly higher (+45,000 feet) than the rest and they don’t need to follow an air route because there is nobody around them. That airspace in uncontrolled to a certain extent and they are free to operate in any direction.

However, at these altitudes, if something happens with the cabin pressurisation, the flight crew and passengers have less than a minute to live if they don’t get their oxygen mask on.

When flying across the Atlantic, you have special corridors with specific entry and exits points.

These corridors are called NATs (North Atlantic Tracks). Everyone crosses over in an orderly way because there is no radar coverage over the Atlantic. Flying needs to be precise all the way across. The only aircraft that didn’t need to use the NAT is the Concorde because it always flew way above the others at 45,000 to 60,000 feet.

Safe travels everyone and stay safe!

Capt. Michel Treskin

Editor’s Note

Do you have a special topic to request in Aviation? Are you curious about anything relating to flight, planes, being a pilot, etcetera? Then reach out to our Senior Editor, Jennifer J. Lacelle, at editor@iinta.ca with subject line: Aviation: Topic Request.