The weapons in Jet mode are considerably less
effective that the weapons in Walker mode.
Couple this with the fact that Jet mode does not
allow the Shield to generate. Only use Jet mode
when you need to blow something up or kill a
Fighter (or any other air units such as bombers,
landers, etc.) in the air. Stay on your side of
the battle, as it will be nice to have a helping
hand when things get rough. Try not to use all
your energy while in Jet mode; when you land you
will have no shield. Repair Pads are your
friends -- use them.