That seems not to be true. The NSA approved it for use by the US Government. It was developed by IBM with input from NSA. Originally, NSA’s contribution was undisclosed, but former IBMer’s who moved on to academia have disclosed the details of NSA’s contributions, which were actually to remove certain cryptological weakness. AES is stronger because of NSA. And, as I said, NSA approved it for U.S. Government, including military, communications. There is no way they would do this if they were aware of cyptological flaws.