Calling Web services

I am about to start using the API, I tested the sample request provided at the doc page:

I get the error Authentication Required however I am sending the basic auth params as indicated:

User: [my username]
Password: [my API key] - it has permissions for FlightXMLVersions: v3

Could you please advice?

The MetarEx function is not currently available on FlightXML 3.0 Beta. You can use FXML2 to receive Metar data for an airport.

use and pass the airport code in with the api call