Hi Alan,
The search box should still search for active flights (as long as they are being tracked at the time of the search). If it is not working correctly for you, would you post/email me the flight info you are searching for and the time you searched it. The search box should also still search airports (via name or ICAO code). We are modifying how the search index is built to speed up client side load times. At the moment, if the search fails to find a result, it is not showing the 'not found' popup as it was before. This should come back soon as soon as we finish the server-side code changes. Note that you can also use a wildcard character when you search (i.e. search for "BAW*" and it will list active BAW flights in the search result box.
Also, you may need to do a hard reload (or clear your browser cache) to get the latest JavaScript source files. Sometimes when we make a server-side change, it takes a few days for some client browsers to get the latest files.