  The production and the subsequent decay of the SM singlet via heavy
vector--like colour triplets and electroweak doublets in one--loop diagrams can
shed light on the recent observation of diphoton excess at the LHC. In this
paper, the $E_6$ GUT is considered in the F-theory setting where the $E_6$ is
broken by making use of the spectral cover construction and by turning on the
hypercharge gauge flux. This paper is based on the results presented in
\cite{Athanasopoulos:2014bba, Faraggi:2016xnm, Ashfaque:2016jha} which will be
reviewed briefly. Here, by following the F-theory approach, akin to
\cite{Karozas:2016hcp, Leontaris:2016wsy, Das:2016xuc}, we present a study of
the flipped $SO(10)$ model embedded completely in the $E_{6}$ GUT but with a
different accommodation of the SM representations in the ${\bf{27}}$ of
$E_{6}$.

General Physics;High Energy Physics - Phenomenology