This problem is so obvious on many of the ipad airs, and I am shocked that apple actually let this enormous flaw out of the gates, and seemingly hasn't fixed it.
I have bought and returned 7 or so airs with the same results for each. All of them had the yellow discolouration... Different serial numbers, manufacturers, batches. My current iPad air doesn't necessarily have a huge load yellow tent, but is slightly yellow, and the right half of the screen is significantly brighter than the left half.
This is not a fluke. This is an inherent design flaw with the new iPad air screen, and was never ironed out before production started. I have also checked out countless iPads at premium retailers, and Apple stores. Most if not all of them had screen flaws of some sort... The bar, the yellow, and sometimes both.
My ipad 3 had a perfect screen. I don't get why apple screwed up so Badly on their flagship model.