Federal safety officials are updating their investigation into the engine failure on a United Airlines plane that sent parts of the engine housing raining down on Denver-area neighborhoods last month.
The National Transportation Safety Board said Friday that a microscopic exam confirmed that a fan blade that snapped off had telltale signs of fatigue — tiny cracks caused by wear and tear.
The safety board says the engine had been used on nearly 3,000 flights since its last inspection.
After the Feb. 20 incident, the Federal Aviation Administration ordered that certain blades on the same model of engine be inspected for cracks before their next flight.
