The time between first flight and public announcement of Black Projects varies wildly:
| Project | First Flight | Publicly Announced |
| U-2 | 1955 | 1957 |
| A-12 | 1962 | 1981 (existence declassified 1976, but not announced) |
| YF-12A | 1963 | 1964 |
| SR-71 | 1964 | 1964 |
| HAVE BLUE | 1977 | 1990 (existence known earlier in aviation press) |
| F-117A | 1981 | 1988 |
| TACIT BLUE | 1982 | 1996 |
| Bird of Prey | 1996 | 2002 |
| X-44 Manta | 2001 | 2018 |
| P-175 Polecat | 2005 | 2006 |
| RQ-170 | 2005 | 2009 |
| RQ-180 | 2010 | still not yet made public as of early 2023 |