  The effects of background line opacity (line-blocking) in statistical
equilibrium calculations for Fe in late-type stellar atmospheres have been
investigated using an extensive and up-to-date model atom with radiative data
primarily from the IRON Project. The background metal line opacities have been
computed using data from the MARCS stellar model atmospheres.
  While accounting for this line opacity is important at solar metallicity, the
differences between calculations including and excluding line-blocking at low
metallicity are insignificant for the non-local thermodynamic equilibrium
(non-LTE) abundance corrections for Fe I lines. The line-blocking has no impact
on the non-LTE effects of Fe II lines. The dominant uncertainty in Fe non-LTE
calculations for metal-poor stars is still the treatment of the inelastic H I
collisions, which have here been included using scaling factors to the
classical Drawin formalism, and whether or not thermalisation of the high Fe I
levels to Fe II ground state should be enforced. Without such thermalisation,
the Fe I non-LTE abundance corrections are substantial in metal-poor stars:
about 0.3 dex with efficient (i.e. Drawin-like) H I collisions and about 0.5
dex without. Without both thermalisation and H I collisions, even Fe II lines
show significant non-LTE effects in such stars.
