The specs sheet says "3x 120 mm or 1x 140 mm", but when you look at this photo of the front of the case, it looks like you could attach at least two 140 mm fans there, and maybe even three. Does anyone know for sure? Thanks!
They says it supports a 280mm radiator in the front, so it has to be able to take two 140mm fans. Maybe they wrote it like that because it takes one additional 140 front fan in addition to the one that comes pre-installed. It's a bit weird.
@Campy and @UsandThem, it is clear that you are both right (of course). Thank you for getting back to me.
I also found another evidence: Hardware Canucks did a video on this case and Dmitri moved the stock fans around in search of the best configuration. Here we can see the top fan installed at the front, for a total of 2.