airways and aircraft separation

In order to keep air traffic flowing smoothly and safely, the nation's air traffic management system has for years been using "airways" in the sky. An airway is a designated space of air through which aircraft are directed to fly by air traffic control. Above 18,000 feet they are referred to as jetways. Picture these as large imaginary traffic lanes or corridors in the sky. This ensures that air traffic travelling in one general direction moves smoothly through the controlled airspace system maintaining a safe distance between each aircraft by having them fly at certain flight speeds and flight levels or altitudes.

These airways are indicated on aeronautical charts and are used regularly by all aircraft large and small flying through controlled airspace. When flying cross-country on a commercial jetliner, that aircraft is actually one aircraft in a line of aircraft heading in the same general direction at the same altitude. This is much like cars on the highway travelling at the posted speed limit while maintaining a 3-carlength distance between the car in front and the car behind while driving along a one-lane highway.

Separation of Air Traffic and Rules

As in all aspects of life there are rules and regulations that affect flying. Some rules are just good common sense practices while others are habits acquired through specific training. All of these rules exist because safety in the skies is the most important consideration of all.

There are some basic flying common sense rules in which all pilots and air traffic controllers are trained. Some are given below.

Spend 70% of pilot time scanning the skies using a series of short, regularly spaced eye movements in 10 sections alternately looking both near and far, horizontally and vertically.
If there is no apparent motion between the aircraft you are piloting and another aircraft, then both are probably on a collision course.
Be aware of your aircraft's blind spots.
Before beginning a manoeuvre, make clearing turns while carefully scanning the area for other aircraft.
When faced with an aircraft approaching head-on, both aircraft are required to alter the course to the right.
When overtaking another aircraft flying in the same direction and on the same course, the aircraft being overtaken has the right-of-way, therefore pass well clear of it on the right.
When two aircraft are converging or approaching from the side, the aircraft to the left must give way to the aircraft on the right.
A general right-of-way rule states that the least manoeuvrable aircraft has the right-of-way.
Over congested areas (city or metropolitan area), aircraft are required to fly 1,000 feet above any obstruction (tall building, for example) within a horizontal radius of 2,000 feet of that aircraft.
Over un-congested areas (rural land, not open water), aircraft are required to fly at least 500 feet above the surface.

For most small aircraft flying outside controlled airspace in good weather, the pilots are responsible for maintaining a safe distance from other aircraft. This is the "see and be seen" principle otherwise known as VFR or Visual Flight Rules. In this mode of operation, a pilot must keep a continual watch for other aircraft in the sky. When flying above 3,000 feet above ground level (AGL), the pilot must follow VFR cruising altitudes given below (or east/west cruising altitudes). The pilot may set his/her altimeter to a standard barometric pressure of 1013mb (29ins mercury). If this is the case, at an altitude of over 3000 ft, the pilot is flying at flight levels. Other aircraft flying at flight levels also have the same altimeter setting, thus there is an accurate separation.

In some countries, such as the USA and France aircraft remain separated as shown below:

Flying a magnetic course of 0 - 179, fly at odd thousands plus 500 feet. For example, 3,500; 5,500; 7,500.
Flying a magnetic course of 180 - 359, fly at even thousands plus 500 feet. For example, 4,500; 6,500; 8,500.

In the UK, the levels are divided up into four sectors.

For jetliners flying inside controlled airspace, pilots are still responsible for maintaining a safe distance from other aircraft. They also must strictly follow IFR or Instrument Flight Rules. In this mode of operation, pilots are flying under reduced visibility and must depend on their instruments for additional guidance and information. Though rules of separation vary depending on the airspace in which a jetliner is flying, in general, air traffic controllers and pilots are required to maintain a horizontal distance of 5 nautical miles between 2 aircraft flying at the same altitude. For altitudes at and below 29,000 feet, vertical separation must be maintained at a minimum 1,000 feet. For altitudes above 29,000 feet vertical separation must be maintained at a minimum of 2,000 feet.