I think it would be better to redefine 90 days in a more precise way. The mean solar day is 86,400 seconds, so shouldn't the rule be re-written as "three take off and landings as sole manipulator of the controls in the preceding 7,776,000 seconds?"
Or should the definition be based on the sidereal day? 23hr 56 min 4.1s instead of 24hr?
Oh but unfortunately day length varies, see
Fluctuations in the length of day - Wikipedia, the free encyclopedia
How should the rule take that into account?