Late 1999
A German news item says that Mohamed Atta, Marwan Al-Shehhi and Ziad Jarrah report their passports had been stolen. The German Interior Ministry says this may have been a plan to clear any record of travel to Afghanistan.
June 2
According to Czech officials, Mohamed Atta arrives in Prague by bus and stays there for 24 hours.
Now, they're all clean shaven, wearing western clothes, match their new passports, and there's no trace of where they had been....except by corroboration.