If an AI file was created in Illustrator and you can’t view it in the preview pane just change the extension to PDF.
This may or may not work if the Illustrator file was created in any other software. This problem happens when other software companies didn’t create the export settings correctly. Most times Illustrator can fix the problem by resaving the file.
If you don’t have Illustrator and if the file was saved to Illustrator V9 or later, then you can use Inkscape to open the file which it can be saved to a different format (ie. .svg, .pdf etc.)
Also, changing .ai to .pdf may help if you are having problems opening .ai in LB