Can my customers pick their own seat on the plane when they book on my portal?

Yes, on many flights they can, but not on all of them. Seat selection works only when the airline shares its seat map with the supplier behind the API, and not every airline does that for every fare. Where the seat map does come through, your customer sees the cabin layout during booking and can choose a window or an aisle in the usual way.

The airline sets the rules, not the portal. Some seats are free, some are paid, and some are held back until closer to departure or until check in opens. When an airline charges for a seat, that charge is passed on to your customer at the time they choose it, and it is only really confirmed once the airline has accepted it. If an airline does not offer seats through the API at all, your customer can usually still choose one later on the airline's own site using the booking reference.

It is worth being careful about what you promise. A seat shown as chosen can still change if the airline swaps the aircraft or reorganises the cabin, which happens more often than most travellers expect. Telling your customer that a seat is requested and normally held, rather than guaranteed, saves an awkward conversation later.

Ask us which of your airline sources return seat maps and which do not, so you know before you sell which of your flights can offer seat choice at the time of booking.