During November 1998 until February 2001 Atta lives in a four room apartment at 54 Marienstraße in Hamburg. He shares this flat with a number of other al-Queda operatives. According to the site, during the 28 months Atta's name is on the apartment lease 29 Middle Eastern or African men register this address as their home address.
It is immediately under surveillance by the German intelligence because of connections to businessman Mamoun Darkazanli that connect to Said Bahaji (one of the two persons on the lease together with Atta).
9/11 mastermind Khalid Shaikh Mohammed visits but despite the fact that he was wanted by the US since 1998 the US apparently fails to tell Germany what it knows about him [New York Times, 11/4/02; Newsweek, 9/4/02].
The CIA also starts monitoring Atta while he is living at this apartment, and does not tell Germany of the surveillance. Remarkably, the German government will claim it knew little about the Hamburg al-Qaeda cell before 9/11, and nothing directed them towards the Marienstrasse apartment. [Daily Telegraph, 11/24/01]
The Washington Post refers to hijackers Nawaf Alhazmi and Khalid Almihdhar when it later reports, “In November 1999, two Saudi Arabian men moved into a ground-floor apartment at the Parkwood Apartments, a town house complex near a busy commercial strip in San Diego .” [Washington Post, 9/30/01] Alhazmi's name is on the apartment lease beginning in November 1999. [Washington Post, 10/01] The Los Angeles Times similarly notes, “A man by [the name Alhazmi] moved to the Parkwood Apartments in San Diego in 1999, according to manager Holly Ratchford.” [Los Angeles Times, 9/15/01] Some reports even have them visiting the US as early as 1996. [Wall Street Journal, 9/17/01; Las Vegas Review Journal, 10/26/01] However, FBI Director Mueller has stated the two hijackers did not arrive in the US until the middle of January 2000, after an important meeting in Malaysia. While some news reports mention that the hijackers first arrive in late 1999 [Los Angeles Times, 9/1/02; Los Angeles Times, 11/24/02] , over time, mentions of the lease beginning in 1999 will slowly fade from media accounts.
And what about Johnelle Bryant...
According to Bryant, who has worked at the government agency for 16 years, Atta arrived in her office sometime between the end of April and the middle of May 2000, inquiring about a loan to finance an aircraft.
Then there is this:
The FBI also told the owners of the Norman flight school in 1999 that the FBI knew then of other pilots who had visited the Norman flight school that the FBI also knew were training for airplane attacks on public buildings including Mohammed Atta as well as Bin Laden’s own personal pilot.
Atta was known to have aliases and false passports:
Spanish police last February arrested Algerians Khaled Madani, 33, and Moussa Laour, 36, on suspicion of furnishing phony passports to, among others, al Qaeda operatives Ramzi Binalshibh and Mohamed Atta. According to a February 29 Associated Press dispatch, Binalshibh revealed Madani's identity to interrogators at the American military prison at Guantanamo Bay, Cuba.
"The CIA also starts monitoring Atta while he is living at this apartment, and does not tell Germany of the surveillance."
First time I've heard of the CIA monitoring the Hamburg cell.