What Was that Formation of UFOs Flying Over Yakima Last Night?

I was outside last night and noticed these crafts flying in formation, pretty low to Yakima by traditional standards, barely making a sound and moving much slower than normal. What were they?

I thought they might be helicopters at first as they were flying about that speed, but I couldn't hear anything and helicopters have that very distinctive sound. I thought they might be planes but they weren't flying as fast as they normally do. They were flying south toward the airport, but not at the right angle to land at the airport.

They could be anything, but as they were unidentified flying objects, we had some UFOs over Yakima.