They've been up for 2 years, so how is it "Now that five years are up, Google would want to deny competitors access to that data"? If that was their reasoning they would've done it 2 years ago. It's 2 years of extra advantage they didn't need to give their competitors, right?
If that was their reasoning, they could do it whenever they were ready and willing after five years. So this explains why they had to do it for five years and might explain why they won't be doing it much longer than that. It might also indicate that cutting off the API was intended but not urgent.
Why would it be so close to the anniversary though? It seems to suggest something else might be going on at the 7-year mark.
Perhaps some people thought you were only nitpicking but I agree and I think it was useful that you asked about this so that we got the discussion leading to a better answer.
Now that the five years are up and Google Flights just started facilitating actual airfare purchases (a recent development)
Okay, that second part finally explains it, thanks for that. I had a hunch the five years having been up 2 years ago didn't tell nearly the whole story (though apparently people think I'm crazy for thinking that).
Well, the question is why did Google wait the 2 non-required years before shutting it down? Seems like something they wouldn’t just forget about.