In the wake of the coronavirus, sports stadiums have fallen silent, shopping malls have been turned into ghost towns, and bars have emptied. But the skies—depending who you ask—have gotten a lot busier.

Hannah Levine was outside with her dog around midnight in April when she saw a curious yellow light glide across the sky and vanish, one that didn’t resemble a plane. Puzzled, she pulled up a night sky app on her phone to check whether it might be a satellite or the International Space Station, but nothing came up.

“I was like, ‘Oh my God, I saw a UFO,’ ” says Ms. Levine, 26, a nanny in the Detroit area. “I mean, it was definitely unidentified.”

With more people at home, this is shaping up to be a banner year for extraterrestrial encounters, according to data from the nonprofit National UFO Reporting Center, which reports sightings this year are up 51% so far over the same period in 2019. Among 5,000 incidents recorded this year, 20% occurred in April as much of the nation remained in lockdown.