It is the biggest disposal undertaken by the organization since its taxpayer-funded bailout in 2008 and comes as the firm focuses on its central retail and commercial banking business.
SMFG had to fight off competition from the China Development Bank and American lender Wells Fargo in order to seal the deal.
RBS Aviation Capital's chief executive Peter Barrett told the Independent: "The fact that this substantial transaction ... has been executed so successfully in such a challenging market is a great testament to the quality of the business."
Some Â£160 billion ($246 billion) worth of assets has been sold off by RBS in the past three years as it continues to reduce its non-core division.
It comes after This Is Money revealed that the government is to cap RBS bonuses that are deemed to be excessive.
By Tony Aynsley