Full FAA Chronology at this link.
19470409: CAA granted its first approval of the Air Forces’ Ground Control Approach (GCA) radar device for commercial planes, authorizing its use by Pan American Airways at Gander, Newfoundland. (See April 3, 1947, and July 11, 1947.)
19670409: The Boeing 737 made its first flight. On December 15, 1967, FAA type-certificated the airliner, a short-range jet transport with swept wings, wing-mounted twin engines, and a maximum capacity of 107 passengers, for operation with a two-man cockpit crew. The plane entered scheduled airline service on February 10, 1968.
19700409: Boeing 727-200 “stretch jets” were allowed to operate at Washington National Airport, initially on a temporary basis. These larger capacity aircraft had been banned in the past to prevent overcrowding of the airport’s terminal building. (See April 24, 1966.)
19970409: FAA established requirements, effective this date, affecting the operations of U.S.-registered aircraft in designated Reduced Vertical Separation Minima (RVSM) airspace. This designation referred to airspace between flight level (FL) 290 and FL 410 – in which a minimum of 1,000 feet separation, rather than the 2,000 foot minimum separation generally required above FL 290, was to be maintained between aircraft. These regulations required operators and their aircraft to be properly qualified and equipped – as well as to obtain approvals certifying these conditions – to conduct flight operations while separated by 1,000 feet. RVSM was to be applied only in designated areas, and the first such area was to include certain flight levels in the North Atlantic minimum navigation performance specifications airspace. (See March 27, 1997; February 24, 2000.)
19990409: Raytheon completed the first of three major system integration milestones for WAAS. Called stability build, the test showed the ability of the Wide Area Augmentation System (WAAS) to provide augmentation to the U.S. global positioning system (GPS) system. During the test, the system operated continuously for 72 hours using WAAS ground and space components. In monitoring the test, Raytheon and FAA examined data from several locations, including Denver, Oklahoma City, and Dayton. The next system integration milestone, the Full Functionality Build, would be followed by the performance build, the final software build designed to show that the system was ready to enter formal system testing. (See January 5, 1999; August 24, 2000.)
20180409: FAA granted a beyond visual line of sight (BVLOS) waiver to Xcel Energy, the first such waiver for utility inspection operations. Xcel planned to operate a small BVLOS helicopter weighing less than 55 pounds within a designated area approximately 20 miles north of Denver International Airport. On September 12, Xcel launched its first such drone to inspect electric power lines near Fort St. Vrain Generating Station in Platteville, Colorado. (See December 28, 2016; August 20, 2018.)