  We embed a flipped ${\rm SU}(5) \times {\rm U}(1)$ GUT model in a no-scale
supergravity framework, and discuss its predictions for cosmic microwave
background observables, which are similar to those of the Starobinsky model of
inflation. Measurements of the tilt in the spectrum of scalar perturbations in
the cosmic microwave background, $n_s$, constrain significantly the model
parameters. We also discuss the model's predictions for neutrino masses, and
pay particular attention to the behaviours of scalar fields during and after
inflation, reheating and the GUT phase transition. We argue in favor of strong
reheating in order to avoid excessive entropy production which could dilute the
generated baryon asymmetry.
