Glock M29 or 1911—both in 10mm
On a folder it's measured from the tip to the hinge end. Having worked airport security in the past I can tell you most screeners use the palm of the hand as a standard of measure. If the blade is smaller than the screeners palm then it's okay to go on board. If not it gets checked. Box Cutters just recently returned to the "okay to fly" lists.