Over the past 13 years, the world's airlines and the world's governments have spent several large fortunes protecting civilian airports, aircraft and passengers from terrorists, hijackers, bombers and other miscreants.
We have searched through and X-rayed billions of bags and patted down, sniffed and scanned billions of people, humiliating many of them in the process.
We have created extensive databases and information systems to investigate and verify the identities of people who travel, at great cost and inconvenience.
And now we are reminded that the most insidious threat to our freedom may not be the odd zealot, shoe-bomber or absent-minded gun collector, but our own inability to live at peace with ourselves.
As of this writing, the emerging consensus in the West is that pro-Russian separatists in Eastern Ukraine shot down Malaysian Airlines Flight 17 using a Russian-made, surface-to-air guided missile, mistakenly believing that they were shooting at a Ukrainian military transport plane.
In light of subsequent events, it's no consolation that this may have been an accident. The activities of the so-called "rebels" at the crash site (one commentator called them "undisciplined louts") and the responses of the Russian government to the whole affair have been hypocritical, cowardly, criminal or all of the above.
In the wake of the disaster, IATA Director General Tony Tyler correctly observed that "nobody should be shooting missiles at civilian aircraft" and called on the world's governments to review "how airspace risk assessments are made."
In addition to assessing risks to the airspace, governments should redouble their efforts to reduce those risks. Aviation has a proud history of learning from its accidents. Diplomats and statesmen should take heed.