RTX began in 1922 in Cambridge, Massachusetts, when Vannevar Bush, Laurence K. Marshall and Charles G. Smith founded the American Appliance Company. Smith’s study of the star Zeta Puppis led to a gaseous helium rectifier that let radios run from wall current instead of leaky acid batteries. The tube was called the Raytheon, and in 1925 the business became the Raytheon Manufacturing Company. In World War II it mass produced cavity magnetrons for radar, making about 80 percent of the Allies’ magnetrons by 1945. That year engineer Percy Spencer noticed a candy bar melting in his pocket near a magnetron, and in 1947 Raytheon demonstrated the first commercial microwave oven, the refrigerator-sized Radarange. From 1948 it built missile guidance and the Lark, Sparrow and Hawk missiles, and in the 1991 Gulf War its Patriot system was shown on live television intercepting Iraqi Scud missiles.

The other half of RTX started in 1929, when William Boeing and Frederick Rentschler of Pratt & Whitney formed United Aircraft and Transport. Antitrust laws after the 1934 airmail scandal broke it up, and the engine side became United Aircraft, maker of the J57 and the JT9D turbofan that powered the original Boeing 747. CEO Harry Gray renamed it United Technologies in 1975 and bought Otis Elevator and Carrier to balance defense cycles. In 2020 UTC spun off Otis and Carrier and merged with Raytheon, renamed RTX in 2023, with $88.6 billion in revenue, 180,000 employees and a headquarters in Arlington, Virginia, since 2022. In August 2024 RTX was fined $200 million for ITAR violations, and in October 2024 it agreed to pay over $950 million to the SEC and DOJ, covering bribes to a Qatari official and $574 million over alleged overcharging on Patriot and radar systems.

• The rectifier tube was marketed as a battery eliminator, and the name Raytheon loosely means light from the gods.
• Raytheon tested its microwave discovery on popcorn and eggs, and later bought Amana Refrigeration.
• Patriot revenues reached nearly $300 million by 2006.
• In the 1990s Raytheon bought E-Systems, Texas Instruments’ defense unit for almost $3 billion, and Hughes Aircraft’s defense business.
• RTX stock rose 77 percent between October 2023 and July 2025 despite protests at sites in Tucson and Louisville.