[Kromm]

To quote p. B370, once you grapple someone, "He may not move away until he breaks free," with one exception: "If you grapple a foe of more than twice your ST, you do not prevent him from moving away." This rule says nothing at all about how the moving away is accomplished: walking, swimming, flying, tunneling into the ground, etc. A character's movement powers have his usual ST + Lifting ST, unless he has bought something like Lifting ST (Accessibility, Only while flying, -30%) . . . which is a really good idea, by the way. Thus, if someone with ST 200 grapples a flying foe with ST 60, the flying guy's Flight pulls up and away at ST 60 and the brute pulls down at ST 200, and this is treated as being no different at all from a ground-bound grappler pulling back and away with ST 60 while his rival pulls in the other direction using ST 200.

All of this is predicated on the fact that ST gives HP, and HP approximate mass. Thus, a being with ST 200 presumably has commensurate mass (c. 500 tons). If he has less mass than that, then he's evidently using "weird powers" – like zero-range psychokinesis, elemental earth nature, or chi – to justify it. It's up to the GM whether those powers can directly oppose other weirdness like wingless Flight and TK; by default, though, they can.

The GM is free to say that someone with ST 200 but just a ton of mass is limited to ST commensurate with mass to resist such things . . . that's about ST 25. But then he has to give out some compensatory benefit for the loss of the value of 175 levels of ST, which was priced assuming that all the ST works even against being airlifted, because the ST comes with mass. One fair benefit would be to say that such a character only counts as having HP 25 when he falls or is slammed into something, which will make such collisions much less painful; in that case, the flying character with ST 60 could lift off with him (ST 25 < ST 60/2), but wouldn't hurt him nearly as much with a body slam (1/8 the damage dice that 200 HP would suggest).

However, it would be unfair to look at the descriptive effects ("I can fly and he can't!"), ignore the You Get What You Pay For rule, and just screw the ST 200 guy out of the value of his ST without giving something in return. One of the things ST 200 does guarantee is being able to keep anyone with under ST 400 from moving away once grappled; waiving that should come with a compensatory benefit. (Starting with a look at the box on p. B352 and noting that such a character should be able to jump as if he had Basic Move 50 . . . and possibly a glance at p. B350, where it's fairly clear that gravity up to 4G wouldn't slow him at all.)