I work for an airline in aircraft maintenance with a wide variety of aircraft. We do A-checks on our fleet about every 6 weeks. We do not do B checks as these have been incorporated into A and C-Checks and this is the case with the majority of airlines for most fleet types. We do C-Checks once every 2 years which take between 3 and 6 weeks provided we do an out of phase inspection every 12 months which takes approximately 5-10 days. D checks are also a thing of the past. Doing an A-Check every week is excessive and a B-Check every month is also. A more realistic schedule would be an A-Check every month, a B-Check every year, a C-Check every 2 years and a D-Check every 8 years if you did not want to remove the B and D checks.
Just a suggestion as I really enjoy the game