Multiple Trip Booking

I have a car service that allows multi-trip online booking.

The user can configure the destinations, date, time, passengers, additional accommodations and choose the car for EACH trip.

My dilemma is that booking, like the checkout process, is a linear task.

It is best for the to user to go from A > B > C And not recommended for them to go from A > A1 > A2 > B > B1 > B2 > C. Since this implies mini task-flows, which confuses the user. (e.g. Clicking "Next" takes from A1 to A2, and not B as expected).

My question is: 1. Have you seen any good implementation of multi-booking processes? I've searched airline websites without much success, they are every confusing to use.

  1. Any other suggestions on how to approach this without making the process feel overwhelmingly long?

Thanks!