Generally, travel agencies should initiate communications with their customers not only during the booking process but also after the trip starts. For instance, once they begin their travel journey you can send them an email wishing them a good and safe trip, followed by a series of other messages informing them about the country and location they are in, the historical sites that they can visit and entertaining activities that could be done during their stay.
To create a welcome automation series, you need to identify the proper trigger. For example, you can ask in a form field the expected travel date when the automation will launch and messages will be sent to each client accordingly.
Then based on the specific date of travel, you can start sending out the first email and add one day delay or two between each email.
** Note: Your automation will not work properly if you do not clearly set up all the required conditions.