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Explainer: when and why is air space restricted?

The downing of Malaysia Airlines flight 17 has led to many questions being asked about the propriety of planes flying over eastern Ukraine. Many have pointed out that other airlines had prohibited their…

Following orders from above. Aero Icarus, CC BY-SA

The downing of Malaysia Airlines flight 17 has led to many questions being asked about the propriety of planes flying over eastern Ukraine. Many have pointed out that other airlines had prohibited their flights from operating in the airspace through which MH17 was flying when taken down. Unfortunately, many of these comments fail to grasp the complexities of airspace and operational regulations.

In general the airspace over a particular country is controlled by that country. It is that country’s aviation regulatory body, such as the US FAA or UK CAA, and the air-traffic control organisations that determine where, when and how aircraft are allowed to fly. On top of the local regulations, pilots and airlines are required to follow the directives of the country in which they are registered. For instance, a British Airways flight flying over the US would be bound by both the rules of the FAA and the CAA. Plus, each airline may set more restrictive rules on their own operations.

Because of this a lot of confusion has arisen as to whether or not specific airlines from specific countries were prohibited from flying over the disputed areas of eastern Ukraine.

Airspace restrictions

Airspace restrictions are generally set up for two reasons: to ensure the safety of aircraft and their occupants and to ensure the safety of people on the ground. In the case of some restricted military airspace, this may be because of training flights or weapons testing.

Restrictions may also exist because the country is trying to protect an asset inside the restricted airspace. A good example of this is the prohibited flight zones in and around Washington, DC, where flights below 18,000ft are generally prohibited without prior authorisation. These were created to reduce the risk that someone would use aircraft to damage or destroy portions of the United States government. While the restrictions existed before the September 11, 2001 attacks, they were revised in response. The same is true of the airspace restrictions over Disneyland in California and Walt Disney World in Florida.

Other restrictions will arise from disruptions to normal aviation services. For instance if the air-traffic control radar at an airport fails, certain types of flights may be prohibited.

The specific details of each flight restriction are published as a Notice to Airmen (NOTAM).

NOTAM issued during an air show in Pasco, Washington state. Federal Aviation Administration, Author provided

These documents tell pilots the location, applicable times and the specific restrictions for each area of restricted airspace. Many of them will also give the reason for the restriction and the consequences that may arise from a violation. For instance, violating the restrictions around airspace over Washington DC may carry civil and criminal sanctions. If the US government perceives that the aircraft is an “imminent security threat”, deadly force may even be used. Plus, permanent restrictions will be indicated on air navigation charts:

Restricted Flight Zone around Washington DC as indicated on a US air navigation Sectional chart. Federal Aviation Administration

What were the restrictions for MH17?

Much has been written about the fact the American FAA, British CAA and Eurocontrol had issued a series of NOTAMS to their respective pilots, airlines and air traffic control organisations about the risks of operating over Eastern Ukraine. Some articles have even insinuated that the region through which MH17 was flying was off limits to US airlines because of the risk of being shot down due to the ongoing conflict between the Ukraine government and separatists militias.

But a careful read of the NOTAMs issued by Ukraine, Eurocontrol, the CAA and the FAA tell a different story – and this is what Malaysia Airlines is pointing to in its defence of its actions.

In all cases flights on the air-traffic routes were permitted so long as the aircraft was operating above 32,000ft. MH17 was flying at 33,000ft when it was shot down.

The reasons for closing the routes below this are not stated in the NOTAMs. But it is reasonable to believe that the restrictions were in place because of military operations in the area and the consequent risk to commercial traffic. Plus, the neighbouring airspace roughly above Crimea is totally restricted. This is because of the fact that both Ukraine and Russia are attempting to provide air traffic control services in the region, greatly increasing the risk of a mid air collision – not because of the risk of missiles.

While it is difficult to determine if Malaysia Airlines improperly assessed the risk associated with flying over the disputed areas of Eastern Ukraine, there was certainly no consensus that commercial flights on established air-traffic routes, flying above 32,000ft in the region, were at risk.

Yes, several authorities recommended caution in planning flights in this region and for frequent checks of new and revised airspace restrictions. But, at the time of the crash, there were no restrictions in place for any commercial flights above 32,000ft in the area where MH17 crashed.

Only now, following this terrible incident, has a NOTAM been issued, closing off all altitudes to US-based carriers. And, many airlines are being more cautious than is currently required of them, with most circumventing Ukraine entirely.

FAA’s NOTAM following the downing of MH17, closing off the airspace where it was shot. Federal Aviation Authority