AWS D17.1  Aerospace Fusion Welding Code is the most commonly used Aerospace cert used today.

Department of Defense Aerospace and Missle Code Mil-Std 2219 requires its welders to comply with D17.1 for welder performance qualification.

I ran across a company on  ebay no less that was doing certs.I found it in the welding section.He looked like his prices were pretty cheap.You take the test,send it to them,an they do the rest.
  monsoon

Hey Lawrence thats my current card  LOL.

Perkbilt 

Thats a pretty "fun" test to take depending on the thickness range you want to certify in.  I am not sure if it can be broke down into different coupons but I think you got to do all of them.   It would not be a cheap test either if you do all the coupons.  For doing a lot of tubing...if you took a standard 6g test that would cover a lot of ground in the type of work your doing I would think and be much cheaper than a full AWS D17.1       6g would be a butt pipe to pipe joint with a groove   set at a 45 degree angle  (cant pull a particular cert out of the air thats just a 6g but I am sure there is one). 

I don't know where you might go in Alabama but check with the local trade schools...the ones around here offer AWS tests to individuals and companies.  Even if they don't offer it there they more than likely can point you in the right direction.  Good luck man.

Give Bill West at Lincoln Electric, Cleveland a call and see what code they are using in the Motor Sports welding class for example.