The time required depends on 1) whether the existing system is being revised or a new system developed 2) the management structure of the air carrier and 3) the number of pilots who will enter the selection system. Generally, a small carrier that is revising an existing system should allow at least 3 months for the revision and validation process. A large carrier can require up to 2 years. Some of the work should be done before the carrier begins hiring, so planning ahead is vital.