I’m not understanding your point, unless you’re saying that that security would be better on an airplane versus customs? If so, I disagree.
I think it would be easier to apprehend a suspect on a plane rather than in a crowded terminal where the perp could run, or do any number of other things, with potentially thousands of people at risk. Strapped into a seat makes you more vulnerable to a couple of guys standing up.
It does not matter, though- it looks like they did not deliberately let him on the plane, if in fact he got on. There is a little cloudiness as to just where he was nabbed.