A common experience is the locking into memory of each detail in one's personal surroundings by a historic event.  Thus, though I was only eight, I cannot forget a cool morning at Lake Elsinore, the smell of the pines, a checkered cloth covering our picnic basket.  I remember sitting impatiently on the running board of the family's Model A, scuffing my feet on the ground, my father shushing me, the radio scratching to pull in a special news bulletin.  It was December 7, 1941.

A proper noun or a place name can suddenly take on a universal meaning, while evoking private remembrances: Pearl Harbor, Watts, Dallas -- no longer cities but collections of recollections. "Challenger" inflicts a familiar ache that won't go away.

"Grand Canyon" became the improbable tragedy in the sky; "Cerritos," thirty years later, the inexcusable.  My thought-life cannot elude the grasp of the latter -- and the honest fact that the last midair collision has not yet occurred.

At about the same time, Aeronaves De Mexico, S.A. Flight 498, a DC-9 carrying 58 passengers and six crewmembers was inbound to Los Angeles International Airport (LAX), completing its short trip from Tijuana, Mexico.

Midair collisions are inexcusable.  The "crowded sky" is a myth.  Go outside and take a look.  There is plenty of room up there.

Nevertheless, conflicts in the sky continue to occur, ironically in clear weather.  Near midair collisions are documented by the hundreds each year, thousands more go unreported.  Right from the start in civil aviation, "see and avoid" was primitive, unreliable. And the stakes are above counting.  Separation of airplanes in the sky -- clear or cloudy -- is best provided by technology on the ground.

During the seventies, after years of haggling, the TCA (Terminal Control Area) finally become a reality in the vicinity of the Nation's busiest airports.  The intention is to separate flights -- controlled from uncontrolled.  To fly inside a TCA, each plane must (a) obtain a discrete transponder code, (b) provide altitude encoding, and (c) comply with positive radar control, even under visual flight rules (VFR).  Like so many other piecemeal solutions, the TCA, as originally deployed, was fatally flawed.

The critical question: What is meant by "inside a TCA"?

There are no chain-link fences in the sky, no lane-markers, no crosswalks and curbs.  A minor navigation error can result in an airplane "busting" a TCA.  Exactly that is alleged to have happened on August 31, 1986.  The Piper, climbing toward the southeast, clipped a corner of the TCA.

Simple, geographical borders define TCAs on radar screens.  Outside the radar room, up in the sky, a TCA has an invisible "ceiling" and also a handful of "floors" bounded by concentric rings.  Thus, three-dimensional shapes form what is popularly described as an "upside down wedding cake."   An aircraft flying above the ceiling or below any of its floors is considered "outside" the TCA just as much as one flying beyond the outermost perimeter, and positive control (the C in TCA) does not apply.  On August 31, 1986, it was perfectly legal to fly above or below the LAX TCA, talking to nobody.  Now get this: unless he or she wanted to obtain a clearance to fly "inside a TCA," a pilot was not even required to have an altitude encoding transponder.

Imagine the confusion for controllers.  Hundreds of aircraft appear on radar screens each day within the borders of the TCA -- as seen by radar.  Controllers routinely watch anonymous blips and data blocks meander all over their screens.  Without altitude information, there is no way to tell if any given flight is even legal.  Think of "stealth technology," here.  There is no assurance of conflict detection, let alone resolution.

The weather on August 31, 1986 was "CAVU," ceiling and visibility unlimited.  Ironically, these are the conditions most conducive to conflicts in the sky. The Piper was flying under visual flight rules (VFR), "squawking twelve hundred."

This book draws its title from a reality pertinent to public safety in its most fundamental form.  Consider this: The original -- and still current! -- transponders are limited to 4,096 codes, just 12 binary "bits."  Pathetically few  The number is merely a vestige of a distant technological past, a time when, for each electronic bit, an airplane instrument had to be equipped with one whole 12AT7 -- a vacuum tube about the size of your thumb.  Now you can put thousands of bits on a flake of silicon so small, a child's sneeze would blow it away.

With enough codes -- a mere 24 bits would provide 16,777,216 codes! -- aviation authorities would surely assign a permanent transponder identification for each airplane, an "electronic license plate," so to speak.  With universal deployment of the ELP, software on the ground would then access tables of fixed data, including type and performance of each and every aircraft.  Today's practice of repeatedly requesting and entering the information into the ATC system uses up critical radio capacity and imposes extra pilot and controller workload.  You might confirm that for yourself by listening in on Channel 9 on your next cross-country airline trip.

A "fail-safe" system would not permit an isolated equipment failure to result in tragedy.  Same for a human error -- either pilot or controller.  Yet, if the plane is squawking 1200 -- an undifferentiated transponder code! -- a radar operator cannot identify the errant intruder.  Not only that but there exists no mandated radio frequency by which to communicate with the unsuspecting pilot to ward him or her off.  The cold truth: air traffic control does not operate as a fail-safe system.

Limiting all VFR traffic to squawk code 1200 was always a bad idea.  By the way, at any given time, the majority of airplanes in the sky are flying VFR.  Squawking 1200 is atavistic and obsolete.  Inside the borders of a TCA, squawking 1200 is horrendously dangerous.

A radar operator sees 1200 in a data block and knows that the corresponding airplane is not operating under air traffic control.  Its pilot is on his or her own, legally responsible to see and avoid other aircraft.  Only the non-1200 aircraft on the screen are complying with instructions from the controller.  No wonder then, busy radar operators effectively shut off the 1200s -- if not electronically, at least mentally.  Trouble is, one or another of the 1200s may be "busting the TCA."  If so, a vital, life-or-death conflict may not be detected and the consequent traffic advisory will not be transmitted to a pilot who is under positive control within the TCA.

In air traffic control, nobody is safe unless everybody participates.

The Aeronaves de Mexico DC-9 was making a routine approach to LAX, descending through 7,000 feet.  Meanwhile, the flight crew ticked off items on the pre-landing checklist, possibly not scanning ahead for traffic, momentarily complacent in the knowledge that radars and regulations are supposed to provide protection -- inside a TCA.

The passengers would be rechecking their seatbelts and stowing their tray tables.  A mile below, families in a suburban city were sitting down for their Sunday meal.

It was eight minutes before noon.

August 31, 1986 was a Sunday.  I went on a morning hike near Saddleback Peak in Southern California.  The sky was clear, except for a column of black smoke in the distant West.

Muttering to myself about the stickers in my socks, I returned to my VW Rabbit convertible and turned on the radio.  The details of that moment are locked into my memory.

Cerritos.