You guys might want to do the following experiment:

1. Start with removing all cookies that end in aircanada.com.

2. Load www.aircanada.com in your browser.

3. Specify Canada - English (or presumably French).

4. You get a page on which there is *NO* box to select flexible search.

5. Enter, say, a trip YYZ - FRA.

At that point, the page should change slightly, and below the "Country of residence" box, a check box appears beside with there is the wording "I am flexible with my dates" and the next line: "If finding a low fare is most important for you"

Replace FRA by YYC, the box and text disappear.