Business aircraft activity has begun to pick up this year, with flight hours improving in all jet categories and Part 135 hours jumping 13.8% in January, according to the latest report from industry analyst Argus.

Business aircraft traffic overall was up 1.7% in January, compared with the same month in 2012. All categories of business jets posted gains, with mid-cabins improving the most at 4.1%. Small cabins followed at 2.1%, while large cabin business jet flight hours tracked with the overall gains at 1.7%.

But at the same time, not all operational categories improved. Fractional operations continue to struggle, down 6.3%, while Part 91 flying was down 2.4%. Turboprop operations, meanwhile, also slowed 0.5% over January 2012.

January flying, however, was up in all categories – operationally and by aircraft type – from December, with the exception of fractional operations. Fractional flights were down 6% from December. Month-over-month, large cabin aircraft showed the greatest improvement, up 7.4%.

The results are tracked through the Argus TRAQPak data, which details serial-number specific aircraft arrival and departure information on all instrument flight rules flights in the U.S., including Alaska and Hawaii, as well as Canada.

The slight overall uptick in January follows a year in which flight activity remained relatively flat. According to FAA data, 2012 ended with business aircraft flights overall up 0.67%. That includes international flights to and from the U.S. Just within the U.S., operations were down in 2012 by 0.26%.

Flight operations had showed signs of improving in the fourth quarter, but December was slower, keeping the overall improvement for the year to less than 1%, notes analyst JPMorgan. “While some companies have reported pockets of improved U.S. demand, sustained improvement should require a more definitive pickup in activity,” the analyst says.