Using serial-number-specific aircraft arrival and departure information on all IFR flights in the U.S. (including Alaska and Hawaii), data provider ARG/US concludes that business aircraft activity was down by 42.5 percent in January this year compared with the same month in 2008. That is the combined figure for all airplane categories and types of operation. Hardest hit was Part 135 midsize jet (defined as mtow between 20,000 and 41,000 pounds) activity, down by 60.4 percent; least affected was Part 91 large-cabin jet (mtow of more than 41,000 pounds) activity, down by 32.3 percent. As a type of operation, fractional led the decline with a drop of 49.6 percent for all frax aircraft combined. The hardest-hit aircraft category among the frax fleet were small-cabin jets (mtow of less than 20,000 pounds), with activity down 59.6 percent. Overall, Part 135 activity was down 47.1 percent, and Part 91 activity was down 38.1 percent.