In my nonfiction book Live Pterosaurs in America, I mentioned the sighting by Professor Peter Beach, in the summer of 2007, near the Yakima River in the state of Washington. Consider part of what he wrote about it:
. . . we saw many . . . flashing lights. I would have assumed that [they] were fireflies but we [don’t] have them in Washington. One of the flashes took off from a big tree overhanging the river and made a kind of flashing coma turn. Many flashes were parallel to the river. . . . there were many fish . . . Prime hunting grounds for fish-eating birds. Only these things fish at night with bioluminescence. At first I thought I was just seeing shooting stars, but they were all parallel to the river and close to the horizon. Next I noticed that when the cloud cover came in, I could still see the flashes. They were under the cloud cover. Whatever they are, I suggest that they are at least unknown to science, night flying, bioluminescent, flying creatures . . .
About a year later (perhaps in the same area) the professor led another expedition, observing the flight of the bioluminescent flying creatures for three hours:
. . . there were two light [flashes] . . . about 50-100 ft., above the river. . . . followed by screeches from about a dozen or so agitated nighthawks in the general area. I think the Rhamphorhynchoids, if that is what they were, were feeding on the nighthawks as the nighthawks were feeding on the flying insects. Bats were also common, but they were fast, made sharp turns, and were relatively small . . .
I know of others who encountered strange flying lights over rivers in the United States, flights that were only just above the water. Even where fireflies live, these flying things are much larger and faster.
See also “Cryptozoology, science, and pterosaurs”