Many new Boeing 737 Max jetliners are still grounded by an electrical problem in a backup power-control unit. The Federal Aviation Administration said Thursday that 106 planes worldwide are grounded, including 71 in the United States. Airlines are waiting for Boeing to come up with a plan for repairing the planes, and that plan would need FAA approval. It’s the latest setback for Boeing’s best-selling plane. All Max jets worldwide were grounded for nearly two years following two crashes that killed 346 people. The planes have slowly returned to flying since December.