Boeing calls for GLOBAL grounding of all 128 777s with same Pratt and Whitney engine that exploded over Denver - as officials reveal United jet 'suffered fractures to engine fan blades' but full investigation could take a year Boeing has called for the grounding of 128 of its 777 planes as US regulators investigate a United Airlines flight whose engine caught fire and fell apart United Airlines said it will halt all flights by its fleet of 24 Boeing 777 airplanes with same type of engine involved in Saturday's emergency landing in Denver United is the only US airline with the Pratt & Whitney PW4000 in its fleet, according to the FAA