I saw this claim (of 8, not 18) a few months ago, in a single column (can't think of the columnist right now. Maybe I can find it later. It has been repeated several times by other writers, but never with any details as to what precinct, what voting list, etc. I remain a bit skeptical. It could be that 8 of them had drivers licenses, and thus, possibly, could have registered under Motor Voter. But I'd feel better if some writer could state the prcinct(s) involved, tell us they had looked at the voter list, etc.
"When they bought their one-way tickets to California, the hijackers identified themselves with a driver's license, as most people do. News reports indicated that most obtained their drivers' licenses in New Jersey, Michigan, Virginia, and Florida. Thus far, no reporter has observed that the hijackers were eligible to vote in state and federal elections, despite the fact that they were not American citizens."
Note that she does not say that they ACTUALLY registered, only that they were "eligible" (her word) to vote (presumably if they had registered under Motor Voter and had not been caught).
In addition, I found a reference from a 2002 article on Congressional legislation introduced to tighten up on Drivers licenses, which states that "8 of 19" of the hijackers had "phony drivers licenses."
The figure "8 of 19" then morphs in later articles into "registered to vote." I am now pretty confident that we have a migration from "maybe could have" from the Ravitch article; to "actually did" in later columns. At least until someone can find a source for the precinct and precinct list.