You can access your $50 companion e-Certificate online in your My Account on alaskaair.com. Go to the home page (www.alaskaair.com), click on the My Account link in the upper right-hand corner and enter your username/Mileage Plan number and password when prompted to do so and click SIGN IN. That should bring you to your My Account homepage, and if it says "Welcome, [your name here]" you're in the right place. On the right-hand side of this page click on the link that says View My e-Certificates and, on the page that follows, you should see it waiting there for you. If you click on the SHOP button next to your e-Certificate, it will take you to the page where you can shop for flights and will automatically fill in the e-Certificate number for you.

Also, unlike the old paper certificates, you only need to purchase your tickets by the expiration date of your e-Certificate - you do not need to travel by then.