Here are some points taken and analysis based on a January 2,1945 article from the New York Times titled, “Balls of fire stalk U.S. Fighters in Night Assaults Over Germany”.

Summarizing the UFO aspects of the article:

The US is conducting night bombing missions over Germany. US bomber crews had been seeing “balls of light” or “foo-fighters” (UFOs) over Germany for about a month, perhaps starting in November-December 1944. The balls of fire “appear suddenly and accompany the planes for miles”. According to a bomber pilot (#1), “There are three kinds of these lights we call ‘foo-fighters’. One is red balls of fire which appear off our wing tips and fly along with us; the second is a vertical row of three balls of fire which fly in front of us, and the third is a group of about fifteen lights which appear off in the distance – like a Christmas tree up in the air – and flicker on and off.” According to the same pilot (#1), “A foo-fighter picked me up recently and chased me twenty miles down the Rhine Valley. I turned to the port side and they turned with me. We were going 260 miles an hour and the balls were keeping right up with us.” According to the same pilot (#1), “On another occasion when a ‘foo-fighter’ picked us up, I dove at 360 miles an hour. It kept right off our wing tips for a while and then zoomed up into the sky.” According to another pilot (#2), “…the lights had followed his wing tips for a while and then, in a few seconds, zoomed 20,000 feet into the air out of sight…I thought it was some new form of jet-propulsion plane after us. But we were very close to them and none of us saw any structure on the fire balls.” The article mentions an AP article from Dec 13, 1944, “the Germans had thrown silvery balls into the air against day raiders. Pilots then reported that they had seen these objects, both individually and in clusters during forays over Germany.”

I found this article to be compelling information about UFOs because:

The foo-fighters were seen multiple times by credible flight crews up-close.

The article includes multiple eyewitness quotes without trying to discount the information as you often see in articles from later years.

There was no known aircraft technology to explain the foo-fighters as described in 1945. And according to the flight crews, the foo-fighters had “no structures”.

The foo-fighters were very maneuverable, keeping in formation with the planes at night, even during a high-speed nosedive. Considering these were seen in 1944-45, it seems no German technology existed to create the “balls of light”, and even if they did, a human radio controller on the ground could not see the planes well enough at night to fly foo-fighters in close formation with the planes near their wingtips for twenty miles, or right off their wingtip while a plane did a dive at 360 miles per hour. And a foo-fighter was able to zoom “20,000 feet into the air out of sight”.

There is an article that includes some of this information at The story of American pilots encountering UFOs over Europe during WWII (taskandpurpose.com), though I like the original article because it includes more eyewitness quotes. This was also when the media seemed curious and had not started to discount UFO sightings.

I suppose it’s possible that Germany had developed piloted UFOs that they were using to track or distract the bombers. That would explain why the foo-fighters didn’t try to ram the planes. But that possibility of WWII German UFO technology would be quite interesting in itself. Perhaps this technology was brought back to the US from Germany after the war and can explain some of the first US sightings such as Washington State, Mount Rainier in 1947. But there were foo-fighter type sightings (though perhaps less frequent) around Japan and other areas during the same wartime period.

Other possibilities of course are extraterrestrial or natural phenomena. But it seems something like wingtip static electricity does not adequately explain a foo-fighter suddenly zooming 20,000 feet into the air out of sight for example.