Nope. They're not holding people for 8 years.

If you're an Arabic-speaking asylee without any identification at all, you're not getting released until the authorities can make damn sure they know who you are. The fact that all the central american asylees that show up with their passports (along with fifty other members of their village who all corroborate each others' stories with intimate knowledge of the specific region of their country in flawless local Spanish) are released doesn't change that.

And this happened pre-9/11. Has anything changed in the country since then? Are airliners as easy to hit?

Yeah - international travel is even bigger, and there's even more people flying into the country from overseas every day. So it's vastly easier to "blend in" among groups of tourists and businessfolks that everyone in the airport has a vested interest in seeing get through smoothly and quickly. If you're a Chinese operative, you're going to be one of the 2 million Chinese people who fly into the U.S. (mostly to west coast airports), rather than one of the few thousand Chinese people who walk across the border. Because if you try to walk across the border without good ID and a good cover story, you're never getting out of detention; and if you have those things, you're just going to fly over like everyone else.