Citigroup was one of four large US banks that flunked stress tests aimed at seeing how they would hold up in a new economic crisis, Federal Reserve data showed Tuesday. Three others -- Ally, Suntrust and MetLife -- also failed the tests, while 15 other large bank holding companies passed the exercise, the Fed said. \"Overall, four of the 19 BHCs have one or more projected regulatory capital ratios (including capital distributions) that fall below regulatory minimum levels at some point over the stress scenario horizon,\" the Fed said. The Fed said the overall positive results for the 19, in the aggregate, \"reflects a significant increase in capital during the past three years.\" \"In fact, despite the significant projected capital declines, 15 of the 19 bank holding companies were estimated to maintain capital ratios above all four of the regulatory minimum levels under the hypothetical stress scenario,\" it said.