  We investigate models of dark energy with purely kinetic multiple k-essence
sources that allow for the crossing of the phantom divide line, without
violating the conditions of stability. It is known that with more than one
kinetic k-field one can possibly construct dark energy models whose equation of
state parameter $\wx$ crosses -1 (the phantom barrier) at recent red-shifts, as
indicated by the Supernova Ia and other observational probes. However, such
models may suffer from cosmological instabilities, as the effective speed of
propagation $\cx$ of the dark energy density perturbations may become {\it
imaginary} while the $\wx = -1$ barrier is crossed. Working out the expression
for $\cx$ we show that multiple kinetic k-essence fields do indeed lead to a
$\wx = -1$ crossing dark energy model, satisfying the stability criterion
$\cx^2 \geq 0$ as well as the condition $\cx \leq 1$ (in natural units), which
implies that the dark energy is not super-luminal. As a specific example, we
construct a phantom barrier crossing model involving three k-fields for which
$\cx$ is a constant, lying between 0 and 1. The model fits well with the latest
Supernova Ia Union data, and the best fit shows that $\wx$ crosses -1 at
red-shift $z \sim 0.2$, whereas the dark energy density nearly tracks the
matter density at higher red-shifts.
