What is required technically to integrate Smart Cross Sell into my site?

You will need to do two things: create a placeholder on your site for the cross-sell widget to appear, and implement a Javascript tag. EAN will provide you with the Javascript tag, which enables you to pass in relevant data points to EAN which are then used to make customer profiling decisions. You will need to map data collected in your transportation product booking flow to the Javascript tag to pass that data through.