U.S. securities are reviewing the watch list and viewing measures that make sure secure air travel, but not all are equal.

Following is the lists.

550,000 individuals are in the database of Terrorist Identities Data mart Environment, this is very largest collation. These databases are collected by intelligence, law enforcement as well as trusted allies can nominate ?know or suspected terrorists?. After 9/11 attack the national Counterterrorism Center maintained it.

Last Friday when Nigerian 23 years old Umar Farouk Abdulmutallab trying to attack an airlines. He approached Detroit; his name was in this database.

About 400,000 individuals are moved onto this list, which is maintained by FBI?s Terrorist Screening Center, after following two requirements are met.

1:- There must be enough biographical and identifying data so that the person is being screened can be coordinated to the name.

2:- There must be enough data to rectify a ?reasonable suspicion? that the specific person is know or preparing to or suspected to be engaged in terrorist activities.

The database is updated in daily bases, almost 400 to 1200 changes such like addition, deletion or changes to the Nation?s terrorist watch list said by Timothy J. Healy, director of the Terrorist Screening Center.