The vast majority of research in the field of operations research focuses on solving problems that arise in the private sector. The usual goal is to optimize an industrial process with the objective of minimizing the total cost or any other economic measure. The humanitarian sector, despite its very different motivation, is also confronted with problems that are very similar to those tackled in the private sector. For example, the hurricane Katrina that hit the coast of Louisiana in 2005 led to a huge logistics operation. Around 1.5 million people were evacuated once the hurricane made landfall. Only in the Louisiana Superdome, more than 26000 people took refuge for several days as the storm came ashore. Keeping a constant flow of supplies (water, food, medicines…) to the shelters demanded a well-developed operational plan and an enormous effort. In cases like this one, the main goal is not to reduce the total cost of the operation, but to provide a reliable and well-timed service. In the last years, these challenging problems in the humanitarian sector have received increasingly more attention.