  Recently, a novel phenomenon is observed for vacuum decay to proceed via
classically allowed dynamical evolution from initial configurations of false
vacuum fluctuations. With the help of some occasionally developed large
fluctuations in time derivative of a homogeneous scalar field that is initially
sitting at the false vacuum, the flyover vacuum decay is proposed if the
initial Gaussian profile of field velocity contains a spatial region where the
field velocity is large enough to flyover the potential barrier. In this paper,
we point out that, even if the initial profile of field velocity is nowhere to
be large enough to classically overcome the barrier, the semiclassical vacuum
decay could still be possible if the initial profile of field velocity extends
over large enough region.
