In 1975 Varig bought Cruzeiro and started to dominate 100% of international market. Thenceforth VARIG and Cruzeiro flew together until 90s, when Cruzeiro brand finally disappeared. But these two airlines shared many more things, even before the purchase.
VARIG was the first airline of Brazil, founded in May 1927 and started operations through Condor Syndikat, who rented Dornier Wal - VARIG's first aircraft. Cruzeiro was the second airline of Brazil, founded in December 1927 as Condor Syndikat subsidiary and operated VARIG's Dornier Wal, after Condor Syndikat take it back. Also, both had German origins and their stories were closely linked. While VARIG remained as a regional airline, Cruzeiro grew and become the second most important airline in Brazil, with flights throughout Brazil and various destinations in South America.
On October 2, 1947 Cruzeiro received authorization to fly to the USA (New York and Washington) and received three Douglas DC-4 to operate the route. The company even made some test flights but wanted  Brazilian government's help. The government did not accept Cruzeiro give up to operate the route. Who won the route was VARIG, in 1952. So VARIG ordered Lockheed Super G Constellation and began flights to New York in June 1955, no longer a regional airline. In 1961 VARIG bought Real-Aerovias-Nacional and in 1965 gained Panair do Brazil's international to Europe, becoming the largest airline in Latin America. Meanwhile Cruzeiro was the third largest in Brazil, behind VARIG and VASP. Beyond that Cruzeiro and VARIG were the only with international routes, which helped a lot financially, as they  received in dollars, a protection against currency fluctuations.
In 1964 started the military regime in Brazil and the aviation market was fully controlled by government. After the oil shock in 1973, airlines worldwide went into financial difficulties. In Brazil the government thought that were too many airlines and should be only two airlines. The government encourage VASP to purchase Cruzeiro and Transbrasil and thus divide the market between Varig (60%) and VASP (40%).
While negotiations between VASP and Cruzeiro continued, VARIG was buying shares of Cruzeiro. Ultimately Cruzeiro had two proposals: VASP with $60 million and VARIG with $80 million. Besides offered a higher value, VARIG had already about 30% of Cruzeiro share.
On 22 May 1975 Cruzeiro's president announced the sale to Fundação Ruben Berta  (VARIG's owner). Vasp reaction was immediate, claiming for redistribution of routes. In the end Brazilian government announced that would not intervene and the important was to reduce the number of airlines. The government also continued to encourage the merger between VASP and Transbrasil, which never happened.
After the purchase VARIG said that Cruzeiro brand would continue operating, but Cruzeiro's fleet was significantly reduced. Cruzeiro's fleet stagnated with eight Boeing 727-100 and six Boeing 737-200. VARIG also use Cruzeiro brand to test new products and services, as  Airbus A300B4. The A300 made great success among the passengers and VARIG also started to operate A300. In December 1982, Cruzeiro also test Douglas DC-9-80 (or MD-80). McDonnell Douglas expected that VARIG liked the aircraft and ordered a fleet to operate domestic and South American routes. VARIG enjoy MD-80, but chose to order only Boeing 737. The MD-80 was returned in 1983.
During 80s and early 90s the Boeing 727-100 were gradually being phased out. The A300B4 were deactivated in 1989. In 1992 Cruzeiro's fleet was only six Boeing 737-200. On January 1, 1993 Cruzeiro officially ceased, but its aircraft could be seen until 1997, when the last Boeing 737-200 was painted in VARIG colors.