# group actions on fibre bundles

Suppose that we have a group $G$ acting on the spaces $E$ and $B$. Suppose moreover that we have fibre bundles $\xi$ and $\eta$ in the following commutative diagram

If $\xi$ is a trivial bundle, i.e. the Cartesian product, whether could we conclude that $\eta$ is trivial as well?

No. let $F$ have a $G$-action, take $B=EG$ and $E=EG \times F$ with the diagonal action. Then $\eta$ is the Borel construction $EG \times_G F \to BG$ so need not be trivial.