What kind of aircraft has two green lights?

What kind of aircraft has two green lights?
Time: 28/12/24 16:55
Location: Derry, Northern Ireland

Apologies if any of this is useless info or I'm missing stuff, I'm not a regular on this sub. I also tried searching online for matching aircraft descriptions but I have no idea what I'm looking for.

Saw what appeared to be a small aircraft with two flashing green lights.
I could vaguely make out a somewhat square-like or angular circle shape, but it was getting dark so difficult to see properly, and we were driving over a bridge towards it so I didn't see it for long, it was travelling in the opposite direction.

At the time I kind of dismissed it and just thought that the two green lights were unusual, it wasn't until I saw a post about how aircraft have a red and a green light that it stuck out to me enough to make this post. This didn't have any lights except for the two green.

The lights weren't far apart like on a commercial plane. They were closer together which leads me to believe it's a smaller aircraft. It was also low enough to be able to make out some of the actual craft.

If it were a drone then it would have to be a big one, and I haven't seen any in my area except those little hobby ones. I don't even know if they are allowed in my area (northern Ireland). That doesn't mean it's ruled out, of course.

There is an army reserve centre nearby but that's a tanker squadron placement, as far as I know. There is also an airport roughly 10 miles out.