5 countries: China, India, Brazil, Indonesia and the USA account for roughly 48% of the worlds population and that is broadly where the main expansion is forecast. Good news if you are a citizen of one of those countries looking to train for one of these careers in the next two decades. However take out a proportional 48% and that million is now down to 520,000.
Pilots and engineers. If you are interested in the former and assuming a rather generous even split, that whittles the figure down by a further 50% to 260,000.
Of the remaining 190 countries (some don't count, and some count more than others in aviation demographic terms,) but for the point of illustration share out the remaining number equally, and you are now down to an average of 1368
Over how many years? 20! That is about 68 a year. Not that stunning really, and these are optimistic figures from a party in whose commercial interest it is to talk up the market.
Of course 68 is no more accurate in any one domain, than a million is as a glitzy number. Rather like winning a million on the lottery being tempered by the fact that you have to share it with 14,706 other winners as well. Statistics are magical versatile things, and rather like beauty, are very much in the eye of the beholder.