A recent experience with a flight booking system lead to me consider a shady, yet profitable business tactic. This is how it would work.

Imagine booking a flight without cancellation options. This appears to be a common practice with airlines when booking "basic economy" tickets these days. For example, Air Canada, the 10th largest airline by revenue, does this. So, without cancellation options supported by your fare, if you decide to cancel, or alter your flight, you are out the cost of your ticket. If you're a crooked business person, you'd be asking "How can I get customers to voluntarily modify their flights?".

Back them into a corner of doubt.

After a customer purchases their flight, send them a confirmation email telling them their payment has been completed successfully, but confirmation with airline XYZ is still in progress. This can create many mixed feelings, including ease, panic, and anticipation. If the flight is within the next couple days, these feelings can intensify as prices increase, and availablity decreases, causing more irrational behavior for the purpose of securing a flight. With these considerations, how about you draw out the time between the customer's booking request and the flight confirmation? This confirmation time could be based off of a couple factors, but most importantly would be the time before the flight departs, and the customer's desire for the flight. If there is a strong desire for the flight, and the flight departs in less than 24 hours, make the confirmation time an hour or two. In this case, the customer is likely to book another flight, cancel yours, and worry about the financial implications of voluntarily cancelling the flight later. Strenghten financial procrastination by having ambiguous refund terms and let them imagine they can gain their funds back somehow.

Although you completely control a customer's funds after a they click "Pay", as dictated by your platform's terms and services, you still want to maximize plausible denialibility against being a crooked platform so you can maintain the reputation for your platform. If a customer returns to your platform to debate the rights to their funds due to a long confirmation time, there is a lot of mayhem you can cause.

• Make it hard for them to contact customer service. For example, if they booked their flight without an account, don't let them contact you. Make it mandatory for them to have an account. Once they make an account, don't provide a way to add a previous booking to their account. This hints at some edge case that the platform develops just haven't considered.
• Offer them platform credits with a one year expiration. Most people take one vacation a year, and the usage of such credits will be unlikely. Even if they do redeem them, they are using your platform, giving you more opportunities to benefit from them.
• Ignore them entirely when they reach out. This is like nuclear warfare, I wouldn't suggest this because, unless you do a background check on each customer, you never know who you'll piss off. Some people may be technically skilled enough to take down your servers. Some people might even have enough social clout to get your platform cancelled.

This should provide enough of a barrier to harvest many smaller transactions. Higher flight fares will of course see customers making more agressive demands for their funds to be returned in a monetary form as opposed to credits or nothing at all. You can politely remind them it's what they "agreed" when the checked the terms and services checkbox.

Shoving customers into such a decrepit corner, ready to collapse on them at even the slightest breeze is demented behavior, and your platform's survival is surely to be tested.