On May 4, 2026, about 1759 central daylight time, a Cessna 421C airplane, N6161X, was substantially damaged during an accident near Kirksville, Missouri. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that during cruise at flight level 200 (20,000 ft pressure altitude) the right windshield failed, which resulted in a rapid decompression of the airplane cabin. Before the windshield failure, the cabin altitude was selected to 5,700 ft with a differential pressure of 5 psi. The pilot disconnected the autopilot and entered a descent. He then reduced engine power, lowered the landing gear, and applied approach flaps. The pilot reported having no airplane flight control issues after the rapid decompression, but there was significant wind entering the cabin from where the right windshield had separated. The pilot subsequently reengaged the autopilot on heading mode as the descent continued. A review of available ADS-B flight track data revealed that the windshield failure occurred about 1759:44, at 20,050 ft pressure altitude and 12.5 nautical miles (nm) southwest of Kirksville Regional Airport (KIRK), Kirksville, Missouri. At 1804:38, the airplane descended below 10,000 ft mean sea level as it continued toward KIRK. The pilot's headset, glasses, and cap were blown off his head during the rapid decompression. After he retrieved his headset from the copilot floor, the pilot reestablished communication with the air traffic controller and declared an emergency. The controller provided radar vectors to KIRK where an uneventful landing was completed on runway 18. The pilot reported that although local emergency crews were waiting near the runway, their assistance was not needed after landing. A local farmer located portions of the right windshield in his field. These windshield portions were brought to KIRK and secured by the airport manager until the airplane was examined by a Federal Aviation Administration (FAA) airworthiness inspector on May 15, 2026. With the assistance of an aviation mechanic, the remaining portions of the right windshield, as shown in figures 1 and 2, support frames, and associated hardware were removed from the airframe and shipped to the National Transportation Safety Board (NTSB) Materials Laboratory, Washington, DC, for examination. The last annual inspection of the airplane was completed on December 15, 2025, at 8,370.9 hours airframe total time (AFTT). The airframe logbook entry for the annual inspection states, in part, “Performed annual inspection in accordance with 14 CFR 43, Appendix D and the Cessna Maintenance Manual.” The logbook entry did not document if the windshield was inspected during the annual inspection. However, the pilot, who was also the airplane owner, reported that his aviation mechanic did not examine the windshield as recommended by Cessna Supplemental Inspection Document (SID) No. 56-10-01 “Pilot and Copilot Windshield Attach Hole Inspection - Acrylic Windshield”. SID No. 56-10-01 stipulates a visual inspection for cracks around the attaching fasteners and to examine the rubber grommets are properly installed and are in good condition. An optical prism inspection is to be used to examine the windshield and its attachment holes. SID No. 56-10-01 cautions that improperly installed and/or deteriorated grommets can allow fasteners to be in direct contact with the acrylic windshield and create cracks, which could “ultimately cause windshield failure in flight while the airplane is pressurized.” The pilot/owner reported that the right windshield was inspected on January 5, 1984, at 1,385 hours AFTT, in accordance with FAA Airworthiness Directive (AD) No. 84-03-04, using Cessna Information Letter No. ME83-33. The FAA issued the one-time (non-recurring) AD to “prevent cracking and possible loss of the windshield”. The AD required a visual inspection of the windshield attachment holes for evidence of cracking and to replace or repair unacceptable windshields in accordance with the criteria and instructions in the applicable Cessna Service Information Letter. On October 6, 2003, Cessna issued Service Bulletin No. MEB03-4 “Pilot and Copilot Acrylic Windshield Inspection” to address previous reports of windshield failures. Service Bulletin No. MEB03-04 stipulates that acrylic windshields be inspected for cracks and the condition of the attachment hole grommets and screws. Acrylic windshields that have been installed over one year or have accumulated 200 hours total time in service required an initial prism inspection within the next 100 flight hours or by December 1, 2003, whichever occurs first. Then, recurring inspection intervals were stipulated by the Cessna 421C Service Manual instructions (every 200 flight hours and annually). Additionally, acrylic windshields with attachment screws or grommets that have been installed over ten years required a screw and grommet inspection within the next 100 flight hours or by December 1, 2003, whichever occurs first. The service bulletin stipulates that if the inspections were not completed by December 1, 2003, all flight operations were restricted to the unpressurized mode. Finally, Cessna 421C airplanes equipped with acrylic windshields with more than 13,200 flight hours were similarly restricted to the unpressurized mode. According to the pilot/owner, the right windshield was original equipment from when the airplane was built by the airframe manufacturer in 1980. Additionally, based on his review of maintenance logbook documentation, the right windshield had never been removed or repaired after it was installed at the Cessna factory in 1980. Based on the available documentation, at the time of the accident, the airplane and its right windshield had accumulated 8,408.7 hours since new. According to the Cessna 421C Service Manual, SID No. 56-10-01, and Service Bulletin No. MEB03-04, an acrylic windshield is to be replaced every 13,200 flight hours. Figure 1. Right windshield after landing. (Pilot photo) Figure 2. Right windshield and support frames after removal from airframe. (FAA photo)