Small black circular craft with triangle "tail-wing"

I was told I could (and should) report my encounters here, no matter how old they are, so here's 1 of a few.
The time is approximate, I remember that I was around 9 or 10 years old and accompanied my mom, as I sometimes did, to my Dad's office at the BNSF Railroad Depot in Bellingham WA.
As we got out of my mom's car to approach the front door of the building, I happened to look up. I stopped my mom and I and just looked up to see a perfect black circle against the gray, rainy backdrop of the Bellingham skies that day. I remember saying, "What's that, mom?" and her replying, "I don't know...maybe some kind of plane?" and just dismissed the sighting.
If you were to hold a pea at arm's length above your head at roughly a 45 degree angle, that would approximate the size. Off of what I'd call the "rear" of the craft (given it's trajectory of traveling NW) I could just make out what appeared to be the "point of a triangle" that looked to me at the time like a tail-wing of a conventional aircraft, but at that distance and the rate of travel (hard to gauge - from my memory it was traveling faster than a standard prop plane) I can't say for sure. I remember wanting to stay outside and watch the craft, but was hurried into my Dad's office so that mom could run other errands.