For the Ukrainian military on a mission. Must be regular, not a 1 off flight. Must be from a Ukrainian base.
Looking at the Newsweek articles in question, it sounds like just hype in hopes of making Ukraine seem like something other than a lost project militarily. The headline: "Ukraine F-16 Speculation Mounts as Russia Loses 8 Fighter Jets in 3 Weeks." Sounds sensational. But then within that article, this further article is linked, with the line, "This brings the total number of Russian aircraft Kyiv claims to have destroyed since February 2022 to 327." These numbers are all sourced to the Ukrainian government, but let's just take them as fact.
8 planes lost in three weeks is roughly 0.38 planes lost per day. 647 days have passed since February 24th, 2022 (the day Russia invaded). 327 total Russian planes destroyed / 647 days = roughly 0.51 Russian planes destroyed per day according to Ukrainian claims. In other words, according to Ukrainian claims, the last 3 weeks have been historically underproductive in terms of Russian planes being destroyed. Ukraine has been underperforming its claimed historic average, not overperforming it. Why would one speculate that a new, highly effective weapon arrived on the field when Ukraine is doing worse than ever at destroying Russian jets according to its own claimed figures? It's not a spike, it's a lull.
It would be disappointing if this question were to be resolved "Yes" without solid evidence of a F16 taking off from a Ukrainian base.
@Prodicus I thought it was a spike relative to the post-stalemate rate, but I could be mistaken.
@Prodicus to be clear I'm not suggesting that the question be resolved as YES without concrete evidence that there have been F-16s flying over Ukraine in December 2023. But that goes both ways. There is a good chance that this statement is true, and it would be disappointing that this question were to be resolved as "No" without a time buffer allowing for more evidence to be looked at.
It makes logical sense for NATO to have supplied Ukraine with a small number of jets for their pilots to practice with over Ukrainian airspace before delivering the rest.
@NathanpmYoung totally up to you, depends what you were going for (I can't really tell). If training counts then the market likely resolves YES already - Ukrainians are training to fly the F-16s already:
https://www.businessinsider.com/ukraine-f-16-training-russia-war-strategy-2023-11
@chrisjbillington Oh they have to be training from Ukraine. Training in the US etc certainly doesn't count.