It sounds like when you say "an AAC project", you're thinking of MPEG-4 ALS [1], which was the codec chosen by MPEG for lossless audio in the mid-2000s and last updated in 2009. Despite ALS being blessed by MPEG, it never achieved much acceptance in the market. Its most direct ancestor was LPAC [2], developed at the Technical University of Berlin; but ALS included improvements from NTT Communication Science Laboratories and RealNetworks [3].
Apple developed Apple Lossless ("ALAC"), a different, unrelated [4] format, which was fairly similar to FLAC, but different in some minor ways (paraphrasing the FLAC dev's own words [4]).