This is a simple little application that lets you locate airports, VORs, NDBS, and other waypoints and have them overlaid on Google Maps, so that you can see just where they are in relation to everything.
You can also enter multiple points and this will connect them. That's useful for checking out the (listed) flight plan for a plane.
Most of the data is only for points within the US. This includes:
Airways (Jxxx and Vxxx) are not present, but they won't give an error if you search for them. They'll just be ignored.
When using latitude & longitude coordinates, the format is very particular. For example, (40.6259908,-74.6702433). Note that there is no space after the comma; including one will cause it to not work.
To see a single point, just put in the identifier of the airport, navaid, or waypoint into the box and click "Find." The map will recenter and zoom to it.
To see a series of points, put them all in the box, separated by spaces. If any of the points can't be found, they'll be listed next to the search box.
For example, you can check out a flight on FlightAware to get its filed routing. Then you can copy that into the box here and see it overlaid on the map, which you can move and zoom, unlike the FlightAware graphic. Just take note that you might want to add the origin and destination airports at the beginning and end, since they're not present as part of the route and might show the flight ending in the middle of nowhere.
There are a couple of reasons not to rely on what you see here. If you're trying to use it for actual navigation, there may be changes to things that aren't reflected here, as well as things that just plain aren't right. If you're trying to view the flight plan of a plane, keep in mind that while each flight has a filed plan, that doesn't mean it'll actually fly exactly that path. Air traffic control can give planes different routings, especially in the vicinity of the origin and destination airports.
If it's an aiport, first check whether its ICAO code requires a "K" prefix you haven't included (for example, JFK airport would be entered as KJFK). If it still isn't found, follow the next step.
If a point can't be found, click the "make a request" link next to it. Remove any points you don't want to request (typos, etc.) and please, please, please, add some additional information so it's easier to figure out what you mean.
If you come across something incorrect, well, there's no good way to let me know that yet. As a workaround, add a point that doesn't exist (something nice and gibberish-y, like "XYXXXZ", is a good bet) and just replace it with the incorrect point (as well as information about what's wrong!) like above.