spngsambigpants,
The fact that a handful of helicopters were circling the area, possibly checking out precisely what you were viewing, is significant.
It may indeed have been a US black projects aircraft. However, there have been sightings of huge triangular shaped UFOs that are much larger than the
relatively smaller US aircraft.
There are a number of ways to tell them apart.
UFOs often:
are completely silent.
stop and hover easily high in the air.
are surrounded by a glow of light.
turn on a dime.
Jet propelled aircraft are not completely silent, cannot stop on a dime high in the air and hover for long periods, and are not surrounded by a glow
of light.
These are some of the ways to distinguish between US black projects aircraft and genuine UFOs.
With the possible exception of coming across a black projects aircraft that uses a form of propulsion other than jet engines.