Whenever I see him flying, it looks like he doesn't fly fast. But I'm just making a guess. So how fast can he really fly?

He doesn't he glides on air currents. According to marvel.wikia (so take it with a grain of salt) he can go at speeds that allow him to NY to LA in just a few hours.

I'm not sure about that answer Tone702 at least anymore anyways. In Darkhawk's early days as a hero he used a grappling hook and would glide yes but now with his new found ability to use different armor suits I thought I remember him flying but don't quote me on that. Also maybe its just me but I guess it doesn't make sense if he supposedly belongs to a secret group called the Fraternity of Raptors that's purpose was guarding the universe back in the day and yet couldn't fly for some reason?? I suppose that could get filed under mysteries we still don't understand about the DK. I for one am still curious to see what's under the helmet.

Well here are the comics that I read which hinted to me at least the possibility of flight. War of Kings Darkhawk 1 and 2

http://www.comicvine.com/war-of-kings-darkhawk-haunted/37-151132/

@jhazzroucher: it depends on which armor he uses he has a armor that's built for speed but his base armor can fly but not at incredible speeds but who knows when he uses his base armor he just got so he has no clue how to use it nor accesses it's abilities but by the time we are at realm of kings he has a good understanding of it but still has a lot to learn.

@jhazzroucher: if u read war of kings u will see that Chris didn't understand how to use the armor but he can fly really fast and even teleport

@bigbadwolfx0 said:

This is truth, before Chris could only glide on air currents but he eventually learned to fly at subsonic speeds the more he used the Raptor Android to his benefit. But now he can easily break light speed in order to breach planetary escape velocities, he used to be able to teleport via stargate to/from the negative zone and back to shorten distances between intergalactic expanses. But he lost that with the re-visitation of his character.