  We consider an important problem in the shipping industry known as the liner
shipping fleet repositioning problem (LSFRP). We examine a public data set for
this problem including many instances which have not previously been solved to
optimality. We present several improvements on a previous mathematical
formulation, however the largest instances still result in models too difficult
to solve in reasonable time. The implementation of column generation reduces
the model size significantly, allowing all instances to be solved, with some
taking two to three hours. A novel application of lazy constraints further
reduces the size of the model, and results in all instances being solved to
optimality in under four minutes.
