Question regarding credit rating

[fsclips]

Hi there. 

I just wanted to find out how exactly the credit rating calculations are timed.

My 4 planes are making about 700.000 profit a day with a Pm of 47%.
I am debt free and have been for a while now, yet I am still on a rating of C. 
How long does a profitable airline have to be debt free in order to get a higher rating?
None of my flights has ever made a loss and every day I collect more money. 
According to the excel sheet dealing with credit ratings I should be AAA or something. 

Is the credit rating only reviewed once a month or more often?

Many thanks. 

Stefan

[airlinemanage]

the credit rating is always reviewed, everyday, or maybe when you have transactions each time. I guess not returning loans is the best way to improve fast, because the more money you have in the bank, the easier the credit rating can improve. In fact, real airlines do not expand fast, maybe this is a side-effect making your simulation more realistic.