We've again made some changes and added new features that are worth mentioning: Staff salaries are now paid daily instead of once a week (to avoid big sudden payments - helps you to keep track on the weekly costs better). B checks are now performed every four weeks instead of only on the last week of each month. The check is performed on the weekday scheduled when the previous check is over 28 days (= 4 wk) old (and a/c is not in C/D maintenance or not for sale). This change is made to simplify things, and it eliminates unnecessary B check warnings, helps in schedule transitions and drops the large spikes in the pax transportation. Base airport rules changed a bit; the bases are now "unlocked" after airline is >180 days old and has 5 or more planes (previously 365 / 10). (Changed mainly for the benefit of tiny airlines.) MD-90 and B717 fleet groups have been combined. (effective in GW2 and GW4) Added McDonnell Douglas MD-90-50 (even longer range variant from the -90-30ER) and MD-90-55 (-50 with extra exits for more capacity), these are both prototype models. (effective in GW2 and GW4)