Yeah the FBI didn't say flatly "it wasn't terrorism", they said it didn't appear to be terrorism. But frankly, if the FBI had come out and said flatly it wasn't terrorism, they are among the VERY first people who WOULD know that, and the first thing they did was check with the FAA and ATC to see what small planes were non responsive, and the FBI likely knew ten minutes after this crash that it was an accident because they knew what plane, but it takes times to release that kind of thing because you need absolute confirmation.
There are a couple nutter "big lies":
They'll complain about the government "ruling out" terrorism immediately after some incident...of course, you'll never actually find ANY incidents where soon after the incident some authority literally says they've "ruled out" terrorism - it's always something to the effect of "at this point, we have no indications that it was terrorism."
The other claim is that in any incident where the perpetrator or person involved isn't INSTANTLY known indicates the name of the person is Arab or Muslim and it's being covered up. Pure nonsense.