The Transportation Security Administration began developing the new system five years ago to make screening more efficient and give passengers more autonomy and control over the pace of their screening. The TSA checkpoint being tested in Las Vegas — initially only for TSA PreCheck customers and only in the English language — incorporates a screen with do-it-yourself instructions for travelers on how to smoothly pass themselves and their carry-on luggage through pre-flight screening with little or no help from uniformed TSA officers. Testing is being done at a unique “innovation checkpoint” the TSA unveiled in 2019 in Harry Reid Airport’s...