The odds are tipping equally in favour of a section 41 failure and a cargo door event (at this point). Very much doubt that it will prove to be a terrorist event but could still conceivably be a TWA800 repeat (however, read on for my clue interpretation). The bit below about the cabin service chief being found still strapped into his seat is interesting and would indicate that the CVR might hold clues to the captain having stipulated that everyone should remain seated - as a result of some unexpected vibration, noise or weird flight characteristics (such as the fuselage beginning to crack up around section 41 - or possibly a cargo door losing seal). So at this point, if it were a quiz show, I'd be going for that as my answer (but favouring the S41 theory). If it was a section 41 event then the evidence should be clear (on the physical debris plus fairly clear accelerometer and control inputs on the DFDR, as well as cabin press loss). It may prove to be another accident where an external view on CCTV might have helped out the flight-crew (inspired them to stop climbing, slow down and even perhaps to have depressurised or reduce the differential).

I am unsurprised that the section 41 Service Bulletins seem to give an option for repair by reinforcement (aka cure) or regular inspection ("inspect and repair"). As the reinforcement repair is likely to be expensive, I am willing to bet that at least 75% of operators of the Classic would have gone for the inspection option. Once a progressive fatigue-cracking flaw gets underway, it can spider-web in different directions as it progresses undetected behind linings and lavatory cubicles etc. At certain points in this process it can become accelerated by stress concentration points seeking out the paths of least resistance and coming together in a joint venture (so to speak). Once those cracks start to "work", you are then the High Plains Drifter in "Marlboro Country". (i.e.  riding high with an undetected cancer that will and must eventually bring you down).

So much for the hubris of those who insist that fatigue cracking can be NDI detected, mapped and predicted via a fatigue index. That process is fine for locating, controlling and doing battle damage repair early on (with stop-drilling and Boron fibre patches), but once it advances to a certain progressive point (the spider web weave) it is most certainly a time-fuse for loss of structural integrity. Each pressurisation and flight cycle would be another nail in the coffin - as the Marlboro Man might well have drily observed at the end. Specifying "regular" inspection for these types of cracks (below)? If you were my Principal Maintenance Inspector and gave me that as your recommendation, I'd tell you that it was you that was cracking up. Boeing might just take a bath on this one. For them, I suspect it's their turn on that AA587 vertical fin roller-coaster of discovery and regret.

Section 41 cracks

Section 41 cracks

Section 41 cracks

Aviation experts have floated several theories for the crash, including metal fatigue, an internal explosion, sudden loss of cabin pressure, a mid-air collision or a military accident."................................but still NOT an encounter with severe weather??

Which might help explain why, "The ill-fated jet's cabin chief was still strapped to his seat when his body was found, puzzling investigators".

NTSB Team Examines the wreckage

Crash Spurs Revamp Of China Airlines

MICHAEL A. DORNHEIM/LOS ANGELES

The search for victims' bodies is occupying the imited recovery resources at the China Airlines Flight 611 crash site, and slowing the retrieval of wreckage and the "black boxes." The flight data
and cockpit voice recorders were located on May 29, but had still not been recovered as of late last week.

Military radar shows debris falling in several different directions, grouped by color, over a 4-min. period (3:27:56 to 3:31:55 p.m.) following loss of the beacon signal (except the dot marked *, which was observed 7 sec. before loss of signal). [Chart omitted]

Investigators are anxious to retrieve them as their beacon batteries may get weak around June 14. Ocean currents and weather also have been hampering recovery from 130-260-ft. depths.

Shortly after the accident, the ASC obtained primary radar data of the falling debris from the military, but it was in a processed form that did not show individual pieces, and it stopped below about 31,000-ft. altitude. The last transponder return indicates the 747 came apart at 33,500 ft. Since then, raw skin returns going down to almost the ocean have been obtained from two civil radars, one
nearby and the other about 150 naut. mi. away.

The new civil data generally confirm the military tracks, which show the debris initially falling in about four different heading groups, including some that are opposite to the airplane's direction, Yong said. But he cautioned that the calculated speed is
questionable because the radar could be hopping between pieces.

China has provided a transponder track to the ASC. It is overall similar to the Taiwanese transponder track with some minor shifts in reported altitude and speed, possibly caused by timing differences. "It shows an altitude dip of 100 meters (330 ft.) 5
sec. before the transponder signal disappears, which we didn't see," Yong said. But neither track shows any rapid maneuvers.

The new skin returns give a more precise location of where pieces hit the ocean. An initial imaging sonar survey shows the major wreckage is in a rectangle about 4 naut. mi. north-south by 5 naut. mi. east-west, surrounding the data recorders, which are at 23 deg. 35 min. N. Lat., 119 deg. 24 min. E. Long. The resolution of the broad search was too low to identify anything, and a higher resolution survey is now being made.

A remote control submersible took pictures of what was suspected to be a large fuselage piece, but it turned out to be a 40 X 10-meter field of smaller debris, including either first- or business-class seats. Most of the recovered wreckage, 454 pieces
as of late last week, has been parts of control surfaces floating on the ocean. These include the vertical stabilizer leading edge and parts of flaps, slats and ailerons.
 

The year-round ocean current of 2-4 kt. makes underwater operations difficult, and the recovery crew will try to take advantage of roughly half-hour periods when the current stagnates, Yong said. The Taiwan Straits are also windy and choppy.

Maintenance records show that the aircraft, tail No. B18255, had its last full heavy maintenance in December 1993. The D check takes place every 25,000 flight hours and was subsequently split into two staggered "mid-period" half D checks, Yong said. The last mid-period D check took place in January 1999 and included corrosion work, though it is not clear whether that meant prevention or repair. The check was done by CAL during a 40-day period. The 1979-vintage aircraft had about 64,800 hr.

The last C check was done in November 2001. "We can't say yet what was done in the C check, but we're looking at it very carefully," Yong said. The Taiwanese Civil Aeronautics Administration principal maintenance inspector for CAL has been
interviewed, and "we are seeing how they comply with all the airworthiness directives, service bulletins, and so on," he said.

A major maintenance item on 747-200s is ensuring that the "section 41" fuselage nose is not weakened by cracks. This can be accomplished by repetitive inspect-and-repair, or by extensive reinforcement that can cost $5 million. "It seems it was done from a first look at the records," Yong said, but it was not clear yet whether it was by inspection or reinforcement. "We haven't gotten further because we are short on people." The ASC will also look at how CAL's other four 747-200s were maintained.