Coupla things, which may or may not be relevant.
Earlier, the Brazilians said they were basing their search round Fernando de Noronha (maybe because they had aircraft there) - but there were also reports that the incident was about 300km from Natal, which is in the same area.
That ties in roughly with something happening 4 hours into the flight, because that seems to be in the same area, rather than closer to Africa.
Finally, I don't think anyone has mentioned the ITCZ, which must be somewhere round this area at this time of year.
sean
airsound