flydubai for reference. Ranging from 18mnths up to 3 or 4 years. Minimum age for upgrade now 28. So a very junior guy can do it in 18mnths, and it has been done on quite a few occasions. However with all the hoops to jump through here and pure luck regarding the simulator assesment markers most guys take between 2-3 years. Many FO's also choose not to upgrade due to the shift in rosters between left and right seat. Company is now starting to force guys to upgrade though. A senior Captain (5yrs ish at FDB) will still not have anywhere near the roster of a 2 yr FO. Company aims to upgrade 6 guys per month but unfortunately reqruiting more and more DEC's. 750 pilots and 55 ish 737's. Currently around 60 Boeings by years end with one new one coming every month for the next few years.