Final answer:
The main difference between liner services and charter services is their scheduling. Liner services are regularly scheduled, while charter services are on-demand.
Step-by-step explanation:
The difference between liner services and charter services is that liner services are regularly scheduled, while charter services are on-demand. Liner services follow a fixed schedule and operate on specific routes, carrying cargo and passengers at predetermined intervals. Charter services, on the other hand, are more flexible and can be booked as per specific requirements.