Believe it or not (it's a Ripley's)

Re the FAA’s contrary  argument in this AD (2019-24-01) – reproduced at the bottom,  below

When you think about it:

a. There isn't much difference conceptually between an airplane suffering an electrical short in a fuel tank with flammable vapours (per TWA800) and the prognosticated situation for MH370 (that was based upon a precursor precedent accident)..

i.e. a sealed flight deck with an undetected oxygen leak. Because the air swap-out rate at height (due to aircon) is so low, any significant leak of oxygen (colourless and odourless) into the flight-deck atmosphere would only need a spark to set it off, once an oxygen saturation level of circa 83% enrichment was reached (NASA guideline). Then you can/likely will have a DDT explosion (Deflagration to Detonation Transition aka flash-fire or flame-front). Typically a DDT flame-front passes very quickly, and is self-extinguishing, although it will cause disabling and eventually fatal injuries. However the scorching effect of that non-flammable, combustion promoting oxidation agent called oxygen will just superficially, and almost instantaneously, "wash over" the flight-deck surfaces, likely tripping a few self-resettable/ redundant circuits - but not necessarily affecting the innate ability of the 777 to fly ever onwards. The visible effect will be a surface scorching only…. however the short duration temperature peak would be sufficient to thermally trip some breakers and cause redundancy swap-overs.

The spark that causes ignition can be as small as a switching transient (i.e. the tiny spark of contact that you get when you use an old toaster for instance).

The Apollo 1 capsule  fire that killed 3 astronauts (Chafee, Grissom and White) was caused by just such a checklist-ordained switching transient in their designedly 100% oxygen environment. My guess is that the EgyptAir Flt MS804 was just such an accident (per the article at https://www.msn.com/en-us/news/world/french-probe-of-egyptair-crash-faults-airline-with-lapses/ar-BBYrfZc )

As we know, and have specifically identified, the Boeing soft-pedal approach to an undercover squelching of this theory (and seemingly just  incidentally addressing the hazard) has involved numerous abstracted AD’s and Service Bulletins affecting the whole Boeing model range (including the 787). The latest AD, you will recall that I brought to your attention earlier this year was quite surprising (777 low pressure conductive oxygen hoses). Boeing had discovered that not all 777 conductive oxygen low-pressure hoses had been properly identified. (AD 2019-25-12). The Malaysian Reports (Final and interim) both started off by claiming that the flawed hoses had been replaced just prior to the MH370 accident. That’s a Ripley’s.

[Docket No. FAA-2016-6144; Product Identifier 2015-NM-088-AD; Amendment 39-21012; AD 2019-24-01]

Request To Withdraw NPRM: Combination of Failures Is Extremely Improbable

Airbus stated that the risk of ignition sources addressed by the NPRM results from combinations of the electrical fault conditions that have been demonstrated to be extremely improbable.

The FAA infers that Airbus would like the NPRM withdrawn. The FAA disagrees with the request to withdraw the NPRM. While the average risk per flight hour of a fuel tank ignition source may be extremely improbable, the actual risk is not evenly spread across all flight hours, and is instead almost completely concentrated on the subset of flights that occur with a latent failure in the fuel tank and experience flammable conditions. For those flights, a single additional failure that causes a hot short onto compromised fuel tank circuit wiring could cause an ignition source. Such flights do not provide an acceptable level of safety. As explained in the previous comment disposition, the FAA considered both average fleet risk and individual risk and determined an unsafe condition existed based on individual risk, rather than average fleet risk. Finally, the proposed requirements in the NPRM are consistent with the FAA's policy for the unsafe condition determinations related to SFAR 88 contained in FAA Policy Memorandum ANM100-2003-112-15, “SFAR 88-Mandatory Action Decision Criteria,” dated February 25, 2003. The FAA provided a detailed response to similar comments and described the FAA's risk assessment in a related SNPRM that addressed the same unsafe condition for Model 757 airplanes, in Docket No. FAA-2012-0187 (80 FR 9400, February 23, 2015); and in AD 2016-07-07. The FAA has therefore determined that it is necessary to issue this final rule.

Fire  (from link)

· The risk of fire is significantly increased when the atmosphere has greater than normal oxygen content.

· This may happen if an oxygen system is leaking into the work area.

· Materials which do not usually burn in air may do so in an oxygen-enriched atmosphere

· The amount of energy required to ignite a material in an oxygen-enriched atmosphere is also reduced

· great care must be taken if individuals are exposed to an oxygen-enriched atmosphere as clothing and hair absorb oxygen. If you suspect this may have occurred, remove all individuals into the fresh air immediately. They must remain there for at least 15 minutes to normalise the situation. The source of the leak must be traced and sealed off.