When John and I were talking about routes, we made a useful discovery. In any of the embedded Google Map files, simply click on the "View Larger Map" link at the bottom. That will open a larger view in your browser of the embedded route. Look on the left side of this larger view.
You should see a "kmz" button and a Google Earth icon to the right of it. Click on the Google Earth icon to fly the route in Google Earth.
Different devices and systems will differ slightly at this point. iPad will give you the option to open the Google Earth file in Google Earth but, alas, I can't make it fly the route. Other systems, like my Windows 7, shows that the file is being downloaded. Once it is downloaded you can click on the downloaded file (usually still visible on the lower part of your screen). That opens Google Earth.
You are not done, however, but be patient. You are almost there! Look under "Temporary Places" on the left column (or pane). Expand the folder. There you will see a "Path" (3 small points in a triangle -- they are supposed to be waypoints). Highlight this path. Then click the "Path" button a little below and to the right. This should start the flyover. (Really)
Try it with the Carcassonne to Trebes Tow Path route listed earlier in this Blog. Remember to click on the "View Larger Map" at the bottom and look for the Google Earth button to the upper left.