Hi Ivan, Thanks for your comment. The +1 1/3 comes from compensating for the brightness of the sky. Using matrix metering, I find I need to dial in somewhere between +0.67 and +1.3 stops of exposure to ensure that the undersides of the aircraft come out. I set the amount based on what the histogram tells me. There were no other adjustments to the exposure in post-processing.
Great shot! It's odd that your exposure bias shows +1 1/3. Unles something is wrong with your camera or you used a thick filter the photo would be greatly overexposed.