Can my customers book a multi city trip on my portal, like London to Dubai and then on to Bangkok?

Yes, most flight booking APIs can handle a multi city trip, so your customer can search one city to the next and then on to a third before flying home, all in one go. On the portal this usually appears as a multi city or add another flight option next to the one way and return choices, and the results come back as one itinerary with one total fare.

How well it works depends a lot on which airlines and suppliers you have connected. Full service airlines sold through a global distribution system are generally comfortable with open jaw and multi sector journeys, and they price the whole thing as a single ticket, which often works out better for your customer than buying each leg separately. Budget airlines are different. They mostly sell one sector at a time, so a multi city trip made up of low cost carriers will come back as separate one way flights, each with its own fare rules, its own baggage allowance and its own ticket. That is how the airline sells it, so the portal cannot combine them into one ticket.

There are practical limits too. Most suppliers cap how many sectors a single search can include, and very complicated routings with long stopovers or a gap where the customer travels overland can return few results or take a while to load. For those unusual trips many agencies still prefer to price the journey by hand with the airline and then record the booking in the software afterwards.

The best next step is to check which flight suppliers your portal is connected to, then run a few searches on the exact multi city routes you sell most often so you know what your customers will actually see.