Almost as soon as the news broke about the shooting down of a Malaysia Airlines (MAS) plane over Ukraine last Thursday, in which all 298 passengers and crew were killed, people began to ask: What was a commercial aircraft doing over a conflict zone in the first place? Was this disaster somehow the airline's fault?
The answer is no - but to understand why, you have to look at the complex realities of modern commercial aviation.
MAS, already world famous because of the missing MH370, appears to have been following all normal safety rules. And the rules governing flights over danger zones, including Ukraine, reflect the balance between the risks inherent in any flight and the efficiency on which the world airline system depends.
In principle, every airline flight can minimise travel time, emissions, fuel burn and overall cost by taking the most direct point-to-point route. In practice, everything about commercial aviation involves making adjustments to that ideal direct routing, all of which is managed by the global air control system.
Before a flight, an airliner's crew coordinates with company dispatchers about any necessary deviations from the desired route. During flight, they make further adjustments - to avoid thunderstorms, for example. They often request route shifts to the north or south, or changes of altitude, to find smoother air or more favourable winds.
On take-off and landing, they must follow carefully structured pathways to regulate the flow into and out of busy airports. They may be assigned dogleg-like "airway" routings through congested corridors. And they must be aware of a variety of restricted, prohibited and military-operation airspaces and other special areas on their flight routes.
For instance, planes taking off to the north from Runway 1 at Reagan National Airport must turn immediately right or left, to avoid the prohibited zone over the nearby White House.
The Federal Aviation Administration (FAA), which has jurisdiction over American pilots and airlines, and its international counterparts maintain constantly updated "special notice" sites of airspace to avoid. The administration's current list urges great caution for flights over hot spots such as Yemen, North Korea and Syria, and it prohibits low-level flights (below 20,000 ft) over some sites in Somalia and Iraq.
Since April, the FAA has flatly prohibited all flights by American carriers over the Crimean region of Ukraine - but not over the region 200 miles or 320 km to the north where the MAS flight was shot down (although some foreign airlines, like Air France, had already adopted curbs on flying over Ukraine more or less entirely).
Such explicit prohibitions are critical, because the entire aviation system works on the premise that unless airspace is marked as off-limits, it is presumptively safe and legal for flight. The airlines want to minimise cost and time by going as directly as possible, and they rely on regulators to tell them where they cannot go.
For an example of how a system functions when it is built on a different premise, consider Chinese aviation. A vast majority of Chinese airspace is military-controlled and usually unavailable to airlines. Thus flights in China take much longer, burn much more fuel and are delayed much more frequently than those in North America or Europe.
Before MH17 took off last Thursday, its crew and dispatchers would have known that a few hours earlier the Ukrainian authorities had prohibited flights at 32,000 ft and below across eastern parts of the country, "due to combat actions... near the state border" with Russia, as the official notice put it, including the downing of a Ukrainian military plane earlier in the week.
So when they crossed this zone at 33,000 ft, they were neither cutting it razor-close nor bending the rules, but doing what many other airlines had done, in a way they assumed was both legal and safe.
Legal in much the way that driving at, say, 63 miles per hour in a 65 mph zone would be. And safe, not just for regulatory reasons, but because aircraft at cruising altitude are beyond the reach of anything except strictly military anti-aircraft equipment.
During take-off and landing, airliners are highly vulnerable: They are big, they are moving slowly and in a straight line, they are close to the ground. But while cruising, they are beyond most earthbound criminal or terrorist threats.
This is why, even during wartime, airliners have frequently flown across Iraq and Afghanistan. The restricted zone over Ukraine was meant to protect against accidental fire or collateral damage. It didn't envision a military attack.
After each crash, disaster or terrorist episode, it is natural to point fingers and say, Why didn't we foresee that specific threat? Thus one attempted shoe bombing leads to a decade of shoes-off orders in airport security lines. The truth is that air transportation, like most other modern systems, could not operate if it fortified itself against every conceivable peril.
Malaysia Airlines, its crew and passengers and the civil aviation system are the objects of this crime and tragedy. The finger- pointing should not be at them, but at the criminals.
NEW YORK TIMES
The writer, a correspondent for The Atlantic, is an instrument-rated pilot.