Not sure if it was Atta, but did find this ...
Despite that, officials in New England maintain that several of the terrorists crossed into the U.S. from Canada using remote border crossings in Maine.Nova Scotia to Maine could land at Bar Harbor or Portland. Since Atta and one other drove south into Portland, on September 10 I believe (photographed in and about stores withing 10 miles of the Portland Jetport), I figure they came in from points north.At least one took a ferry to Maine from Nova Scotia, they say. And at least two of the hijackers crossed the border at Coburn Gore, Me., where a single immigration inspector usually takes care of everything that passes by on the two-lane road outside.
http://billstclair.com/911timeline/2001/torontostar091501.html <-- Link
I believe this has been disproven since then. Let me see what I can find ...