compete.com does not measure actual visitors the way Google Analytics does. Their panel [1] is "combining the online behaviors of millions consumers" and based on the sites they visit they "... use algorithms and advanced analytics techniques to make projections of US Internet activity to report on the number of individual people visiting a site."

So they do not know the exact traffic on milepoint or flyertalk. They are extrapolating a guess as to the total traffic on those sites. In fact, many sites I've seen on there, where I can compare their numbers with actual numbers are usually not even close. The recent uptick in reported visitors probably has to do with a change in the people on their panel rather than a sharp change in visitors to either site.

[1] https://www.compete.com/about-compete/our-data/