  Supergiant Fast X-ray transients are a subclass of high mass X-ray binaries
displaying a peculiar and still poorly understood extreme variability in the
X-ray domain. These sources undergo short sporadic outbursts (LX ~ 10^36 -
10^37 erg/s), lasting few ks at the most, and spend a large fraction of their
time in an intermediate luminosity state at about LX ~ 10^33 - 10^34 erg/s. The
sporadic and hardly predictable outbursts of supergiant fast X-ray transients
were so far best discovered by large field of view (FOV) coded-mask
instruments; their lower luminosity states require, instead, higher sensitivity
focusing instruments to be studied in sufficient details. In this contribution,
we provide a summary of the current knowledge on Supergiant Fast X-ray
Transients and explore the contribution that the new space mission concept
LOFT, the Large Observatory For X-ray Timing, will be able to provide in the
field of research of these objects.
