Replying to Quick Heli Pro Question

First of all anyone that lives near and REI, and is interested in a Dakine Heli Pro, they are selling the pack for 39.93. I checked on the system the other day, and there are still quite a few Heli Pros floating around in random REI's across the country, and you can order them if you are interested. Second of all.... What is the giant strap that begins and ends right by the top hand loop's purpose? It's really long, and you can actually detach the strap from the bag because it has buckles on both sides. What is this for? Thanks!

Chris