June 15, 2015 10:15 AM EDT

People in the New York City area have been tweeting about planes writing “Justin Bieber Is a Smileophile” in the sky on Sunday. What does it mean?

Maybe it is a publicity stunt. Maybe it is the work of some diehard fans. Maybe these diehard fans are trying to rehab his image after a streak of bad behavior made headlines.

Just watched some planes write Justin Bieber is a smileophile over downtown nyc. What even. pic.twitter.com/e3rfcJnnJy

— Alexander Supertramp (@hushlaa) June 14, 2015

It is a mystery.

Read next: Cursing Bill Clinton and 11 More Best Moments of ‘Bad’ Justin Bieber

Write to Olivia B. Waxman at olivia.waxman@time.com.

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