Here are the two flight paths — at 400 knots and 450 knots:
https://www.facebook.com/178566888854999/photos/pcb.740971779281171/740971732614509/?type=1&theater
If you calculate a 350 knot flight path it would be right where they are searching now — where the 811 Arc crosses the S20 Parallel — a shorter distance from waypoint IGREX where it turned south.
If the red line is where it would have run out of fuel at after 5 hours @ 400 knots, then it would have still had fuel after 5 hours @ 350 knots.
The slower speed and shorter distance from IGREX to the new search area means increased likelihood that there was still fuel in the tank when it went down.
I see what you mean (and fuel in reserve opens up a whole new can of worms).
Are we using 30-35k altitude as a constant between IGREX and spash? 350knots is abt 2/3rds of 'usual' cruising speed at 35K, isn't it? not sure if that would mean anything.