  We discuss inflation models within supersymmetry and supergravity frameworks
with a landscape of chiral superfields and one $U(1)$ shift symmetry which is
broken by non-perturbative symmetry breaking terms in the superpotential. We
label the pseudo scalar component of the chiral fields axions and their real
parts saxions. Thus in the models only one combination of axions will be a
pseudo-Nambu-Goldstone-boson which will act as the inflaton. The proposed
models constitute consistent inflation for the following reasons: The inflation
potential arises dynamically with stabilized saxions, the axion decay constant
can lie in the sub-Planckian region, and consistency with the Planck data is
achieved. The axion landscape consisting of $m$ axion pairs is assumed with the
axions in each pair having opposite charges. A fast roll--slow roll splitting
mechanism for the axion potential is proposed which is realized with a special
choice of the axion basis. In this basis the $2m$ coupled equations split into
$2m-1$ equations which enter in the fast roll and there is one unique linear
combination of the $2m$ fields which controls the slow roll and thus the power
spectrum of curvature and tensor perturbations. It is shown that a significant
part of the parameter space exists where inflation is successful, i.e., $N_{\rm
pivot} = {[50, 60]}$, the spectral index $n_s$ of curvature perturbations, and
the ratio $r$ of the power spectrum of tensor perturbations and curvature
perturbations, lie in the experimentally allowed regions given by the Planck
experiment. Further, it is shown that the model allows for a significant region
of the parameter space where the effective axion decay constant can lie in the
sub-Planckian domain.
