I'm not sure if this is relevant to this post, specifically. However, since we are on the topic of travel affiliate programs.. heh ..let me rant on a lil more.
Some folks have suggested to "sell" info products (e.g. ebooks, e-reports) if you have a Niche Travel website that might also be listing or selling air tickets, hotel rooms and tours, etc. They figure that since people are visiting are already in a frame of mind to "travel", that they might pick up an ebook or eguide as a "by-the-way" (did Frank K*ern popularize this term

?) purchase. If you accept this idea, then you can add c*lick*bank and pay*dotcom.c0m to "providers" of products which can earn you affiliate commissions. Other folks have suggested having CPA zip/email submits as a popup or as a link on your travel niche content website, so that you might earn some easy cash when visitors are "researching" their travel options.
I figure you could probably chuck in travel insurance products, pack backs from A*mazon (as an Amaz*on affiliate), maybe have an e*bay auction page too, on travel stuff (even air tickets) ...
warning.. this paragraph is just my ranting

.. so read critically and with a pinch of salt
Cheerio