Travel customers do not churn, they simply are not asked again
A traveller who had a good holiday rarely decides to leave you. They just come back, get busy, and eleven months later start planning the next trip with whoever is in front of them, which is usually an advertisement or a friend's recommendation. The agency that sold them a delightful trip is frequently not in the conversation at all, because it made no contact between the return flight and the next season.
So retention here is a timing discipline. Two contacts do most of the work: one shortly after the return, while the experience is vivid and referrals are easy, and one at the point in that household's own annual cycle when planning normally begins. Everything else on this page is refinement.