Actually there's no fixed number. It all depends on the batch intake and how many people are qualified for it.
One batch intake may contain people from various interviewing batches. Some have more qualified ones and some don't. So there's no fixed number to it actually because it would be unfair to assess that way.
For example,
A group of 80, if only 10 are chosen and there are actually maybe 20 qualified candidates. 10 qualified ones would be kicked out. The second interviewing batch of 80, maybe only 3 are really qualified. They can't possibly pick 7 unqualified ones to fill the numbers. it would do the company injustice and unfair to those from the first batch that were actually qualified but kicked out.
Therefore, all are taken into consideration. That's why some people receive later replies than others.
Just be yourself, try your best and hope for the best.
By the way, I am sure you all have the passion to fly. But don't just say it. Show it. There are lots of applicants that claim they have the passion but they have nothing to show. Knowledge can be built up easily through reading. But passion doesn't happen overnight. Just a point for you guys to take note of.