There was an argument on Slate, against the fire theory. Here's an excerpt:
Goodfellow’s theory fails further when one remembers the electronic ping detected by the Inmarsat satellite at 8:11 on the morning of March 8. According to analysis provided by the Malaysian and United States governments, the pings narrowed the location of MH370 at that moment to one of two arcs, one in Central Asia and the other in the southern Indian Ocean. As MH370 flew from its original course toward Langkawi, it was headed toward neither. Without human intervention—which would go against Goodfellow’s theory—it simply could not have reached the position we know it attained at 8:11 a.m.