NTSB Identification: CHI07LA06314 CFR Part 91: General AviationAccident occurred Friday, February 02, 2007 in Cape Girardeau, MOAircraft: Raytheon Aircraft Company B200, registration: N777AJInjuries: 2 Uninjured.This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.On February 2, 2007, about 1030 central standard time, a Raytheon Aircraft Company B200, N777AJ, sustained substantial damage during an uncontrolled descent and recovery from cruise at flight level 270. Visual meteorological conditions prevailed at the time of the accident. The flightcrew reported that they depressurized the airplane after noticing cracking of the airplane windshield. They then donned their oxygen masks but were unable to obtain oxygen from the oxygen system resulting in their loss of consciousness. They later regained consciousness, recovered from the descent, and landed without further incident at Cape Girardeau Regional Airport, Cape Girardeau, Missouri. The 14 CFR Part 91 flight was operating on an instrument rules flight plan. The pilot and copilot were uninjured. The flight originated from Rogers Municipal Airport-Carter Field, Rogers, Arkansas, at 0939.On-scene inspection of the airplane noted that approximately 2/3 of the left horizontal stabilizer and elevator were separated from the aircraft and 2/3 of the right elevator was separated but attached at the inboard hinge. The left and right wings were wrinkled. The left pilot windshield outer and inner ply were intact. The inner ply exhibited a shattered appearance with a crack at the lower right hand corner of the windshield. The cabin pressurization dump switch was in the dump position.The oxygen system worked when it was functionally tested in accordance with Airplane Flight Manual. Reply