double friction = P_GetFriction (mo, NULL);
double currentspeed = mo->Vel.XY().LengthSquared();
if((!(mo->Z() > mo->floorz) && !(mo->flags2 & MF2_FLY) && !(mo->flags2 & MF2_ONMOBJ)) // Only apply friction if on ground,
|| currentspeed >= 49.) // or if travelling faster or equal to running speed while in midair -Blastfrog
{
    mo->Vel.X *= friction;
    mo->Vel.Y *= friction;
}