US regulators have announced an investigation after a detached engine cover caused a Southwest Airlines’ Boeing 737-800 to return to the airport soon after take-off. In the latest incident involving a Boeing aircraft, Southwest Flight 3695 was bound on Sunday for Houston Hobby airport with 135 passengers and six crew members aboard. The aircraft had climbed to about 10,300 feet (3,140 metres), but it then returned safely to Denver International Airport and was towed to the gate. No one was injured in the incident. According to the US Federal Aviation Administration (FAA) statement: “The crew r…