same speed as the earth turns under you, whatever that is. (It will vary according to latitude.) I once flew north of the Arctic Circle at midsummer. I left Gatwick after dark but as we got further north the sun started to rise again - in the west.
A bit pedantic, but to add to jno's post, it would have to be in the same direction, (east to west) and at the equator your speed would be roughly 1,000 mph...
The time of year is also a factor. At the North or South Pole the Sun circles the horizon in 24 hours during vernal and autumnal (spring and fall) equinoxes.