import flash.filesystem.FileMode;
      import flash.filesystem.FileStream;
      import flash.filesystem.File;
       
      var myFile:File = File.appResourceDirectory; // Create out file object and tell our File Object where to look for the file
      myFile = myFile.resolve("mySampleFile.txt"); // Point it to an actual file
       
      var fileStream:FileStream = new FileStream(); // Create our file stream
      fileStream.open(myFile, FileMode.READ);
       
      var fileContents:String = fileStream.readUTFBytes(fileStream.bytesAvailable); // Read the contens of the 
      fileContents_txt.text = fileContents; // Display the contents. I've created a TextArea on the stage for display
       
      fileStream.close(); // Clean up and close the file stream

http://office.realeyesmedia.com/blogs/john/index.php/2007/05/26/reading-a-file-with-actionscript-3/

Found this code. It is an example of loading and reading different file types with ActionScript 3

Reading Different File types with AS3

file, actionscript, 3

ActionScript 3