When a heavier and a lighter aircraft descend side-by-side from the same cruise altitude, the lighter aircraft will have a slight advantage until they get to lower altitudes where the heavier aircraft has the advantage.
HazelNuts, does the above explain the very slight variation of speed for max L/D between mach .2 and mach .8 shown in your graph? And if so, can you give an explanation of why max L/D occurs at about mach .5, and not mach .2 for example. I realize this is for a particular jet, however that the value peaks, then falls, as mach increases seems odd to me.
Secondly, I am amazed that over the same range of mach numbers, .2 to .8, the aoa for max L/D will vary from an initial value of 6 degrees (I'm assuming that degrees is the units), to a value of about 2.5 degrees, all while keeping a near constant max L/D of 22. Are you able to comment on this?