Thanks and no problem. However...

Any aircraft change? BA aircraft change? BA LH aircraft change? BA LH aircraft change between London and NY? BA LH aircraft change between specific London and NY airports? etc., etc., etc.

What constitutes a change? 747 to 777 obviously. What about 772 to 773? What about 772 12 F seats to 772 14 F seats? 77D to 77E?

See what I mean? This is a bit like the answer to "Life, the Universe, and Everything." Now we know the answer is 42, what is the question? You have provided a very specific answer (to three decimal places, which seems a little extreme, I would imagine the natural variance would dictate a little less precision than that!) but to which question(s)?

Also, 70ish percent seems rather high to me (although I'm not too familiar with the LON-NYC flights - if that's what you are calculating.) That means for just over two thirds of flights (bound by the actual question you are answering) one isn't going to end up on the plane type you booked, if you booked a year out. Is that correct?

I don't need to see your formula, but I would like to know what your formula is calculating.

rb211.