The Game of Thrones fan site Watchers on the Wall Tweeted a photo purporting to show Harington arriving in Northern Ireland capital.
In a blog post, Watchers on the Wall claims that the photo was snapped by a reader who happened to be on the same flight as Harington. The post also notes that it didn't appear that Harington had cut the long hair he sported while portraying Jon Snow.
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"For those of you deeply invested in #HairWatch, Harington was sporting a man-bun," the post read.
The sighting has fueled additional rumors that Harington's character may yet return to the show despite assurance from one of the show's frequent directors that the character is "a dead man."
On Sunday, Emilia Clarke, who plays Daenerys on the show, posted a photo to Instagram showing her enjoying the sights in Belfast alongside Nathalie Emmanuel, who plays Missandei.