Methane Cloud?

Saw just a real short clip of something on the Disc channel tonight
about how methane clouds affect aircraft. Lower pressure causes the
plane to drop because of reduced lift, and the altimeter to read a
climb because of the pressure change. I think this show may have been
in the context of bermuda triangle stuff. Maybe Im just out of the
loop but I had never heard of this happening (flying into a cloud of
methane I mean). They seemed to have some pretty reputable people
talking about it. Anyone experience this or hear of it?