In the 1970s the jet engine manufacturers found that their products for the commercial (airline) market had been commoditized to a greater extent than in previous decades. Leaving behind a tradition of mating airframes to particular engines (which linked the profitability of an airframe model to that of its exclusive engine supplier), the airframe builders began offering multiple brands of engines. Producers had to compete on service, warranties, and eventually even by buying entire aircraft and then leasing them to the airlines.