Completeness of trajectories of relativistic particles under stationary magnetic fields

The second order differential equation $\frac{D\dot\gamma}{dt}(t) = F_{\gamma(t)}(\dot\gamma(t)) - \nabla V(\gamma(t))$ on a Lorentzian manifold describes, in particular, the dynamics of particles under the action of a electromagnetic field $F$ and a conservative force $-\nabla V$. We provide a first study on the extendability of its solutions, by imposing some natural assumptions.