Washington, Jan 6 : Alaska Airlines has grounded all of its Boeing 737-9 aircraft after one such plane had to make an emergency landing in Portland, Oregon, with a window and a part of the fuselage missing. "Following tonight's event on Flight 1282, we have decided to take the precautionary step of temporarily grounding our fleet of 65 Boeing 737-9 aircraft," Xinhua news agency quoted Alaska Airlines CEO Ben Minicucci as saying in a statement late Friday night. Boeing said in a separate statement that a "technical team stands ready to support the investigation". The plane carrying with 171 guests and six crew members and bound for Ontario, California, took off at 4.52 p.m. on Friday evening and returned to Portland 20 minutes later. According to photos sent in by a passenger, a large part of the airplane's fuselage and a window was missing. The Alaska Airlines Flight 1282 returned safely to Portland International Airport after 'the crew reported a pressurization issue', CNN quoted the Federal Aviation Administration (FAA) as saying. Both the Portland International Airport and Alaska Airlines had confirmed the emergency landing. Kyle Rinker, a passenger on the flight, told CNN that a window popped off shortly after takeoff. 'It was really abrupt. Just got to altitude, and the window/wall just popped off and didn't notice it until the oxygen masks came off,' he added. The FAA and National Transportation Safety Board have announced that they will investigate the incident. /IANS