A fire takes out a wire bundle, shorting the ACARS system, transponders, etc.. The pilots could've been unaware of the fire until it had already compromised the wiring. Even if the transponder knob is in the 'on' position, it may have been disabled due to a fire.. And etc..
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The pilots could’ve been unaware of the fire until it had already compromised the wiring
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One of his main points was that the left turn was made because of a fire .... heading for the nearest suitable airport. The air strip that lined up with the new lat/long heading keyed into the FMS had an over water approach - the airport of origin had a couple of ridges to fly over that could have been problematic with a crippled plane.