  In the settling accretion theory, which is applicable to quasi-spherical
accreting slowly rotating magnetized neutron stars with X-ray luminosity
$L_x\lesssim 4\times 10^{36}$~erg/s, bright X-ray flares ($\sim
10^{38}-10^{40}$~ergs) observed in supergiant fast X-ray transients (SFXT) may
be produced by sporadic capture of magnetized stellar-wind plasma from the
early-type supergiant. At sufficiently low steady accretion rates ($\lesssim
10^{15}$~g/s) through the shell around the neutron star magnetosphere at the
settling accretion stage, magnetic reconnection can temporarily enhance the
magnetospheric plasma entry rate, resulting in copious production of X-ray
photons, strong Compton cooling, and ultimately in unstable accretion of the
entire shell. A bright flare develops on the free-fall time scale in the shell,
$R_B^{3/2}/\sqrt{GM}\sim 10^3-10^4$~s ($R_B$ is the classical Bondi capture
radius), and the typical energy released in an SFXT bright flare corresponds to
the mass of the shell.
