Just curious, why did you expect these keywords to convert well? Is this based on previous experience or your client's personal guessing?
Also have you been tracking how Google handles the serps for your keywords? You mention you are in the travel industry, recently Google has been experimenting with displaying Google Hotel Finder at the top of the serps that could siphon away the higher converting traffic. Even if Google does not show their hotel finder, there are many different parts of the universeral serps that could siphon away conversions like local listings.