The cargo fire hypothesized by Canadian pilot Chris Goodfellow to explain the disappearance of Malaysian Flight 370 (see “Malaysian Flight 370: Canadian pilot’s analysis goes viral“) is a reasonable one.
According to Malaysian officials, the plane was carrying 440 pounds of lithium batteries. Lithium batteries, sitting inert (not being charged or discharged), were identified as the cause of the fire and resultant 2010 crash of a UPS 747 flight at Dubai. Ironically, even though “improper storage” in that case was determined to be the cause of the fire, I have never read any explanation of how improper storage can ignite a lithium battery. It appears more likely that lithium batteries, under certain conditions not completely understood (e.g. a combination of battery construction and chemistry, heat, vibration, and/or shock) can spontaneously ignite, albeit very rarely.
In addition to pilot Goodfellow’s comments, an added interesting point is that Flight 370 also gained very high altitude shortly after communications ceased. It could be that the pilots, upon becoming aware of the fire at that time, tried to quickly elevate the plane to quell the fire by starving it of oxygen. This might have been an excellent maneuver for most fires, but lithium batteries, once ignited, create their own oxygen and will continue to burn at high altitude.
Bottom Line: Until the cause of the disappearance of Flight 370 is positively determined, the possibility of a lithium battery fire is a reasonable hypothesis, and worth investigating.