Originally Posted by darthbimmer

Number of IRROPS per 10k miles flown is the wrong way to count it. Flying long haul routes like transpacific or Europe-Western US, 10k miles is less than one RT, and IRROPS are uncommon on these routes, at least IME. But on short haul routes 10k miles could be 10-15 RTs, and these are more likely impacted by IRROPS. Then, too, there's locality and seasonal factors: summer thunderstorms in the midwest, winter snowstorms in the midwest and northeast, etc.