https://en.wikipedia.org/wiki/Aircraft_hijacking cites two figures for the U.S. rate of hijacking attempts near its peak. The higher one is "Between 1968 and 1977, there were approximately 41 hijackings per year." meaning once per 9 days, an order of magnitude below yours. The other is once per 13.3 days over 1968-72. If both Wikipedia numbers are reliable then the peak must be somewhat higher than 1/9 in 73-77.
I already said ID is not security. How many 70s hijackers got away unidentified? How many would not have even tried if they also had to show ID? I can think of one case, "D. B. Cooper".
This conversation just doesn't seem promising. Your initial wildly-off claim got me worried I might misunderstand the world by that much (I remember the 70s, fuzzily). I wasted time checking it, wondering if the actual peak might be in a year not mentioned, trying to find the paper Wikipedia cited: it was a non-open-access paper with at least four links to check; one of them did show the first page, which at least gave the figure in question, if not the ultimate source.
