The regular spacing of these marks as shown the picture, is consistent with the application of constant magnitude stress cycles, or the pressurization cycles (once per flight cycle). These marks are more closely spaced near the flat-fracture fatigue area than away from the main fatigue area. These incremental crack growth indications were observed as far forward as approximately STA 2055 (outside the covert of the repair doubler) and as far aft as STA 2140 (hole 56).