Why a ‘No Fly List’ Aimed At Terrorists Delays Others

Tuesday, April 22nd, 2003

Why a ‘No Fly List’ Aimed At Terrorists Delays Others explains how poor name-matching algorithms are turning the No Fly List into a serious pain for certain travelers — every time they fly:

The No Fly List, quietly introduced after the Sept. 11 terror attacks, is designed to keep suspected violent types off airliners. It includes terrorism suspects thought to pose an imminent danger to flights. Some people who present a general threat to air safety because of violent behavior also make the list.

But the system comes up with an alarming number of “false positives” — often because the name-matching techniques were designed “to let agents find passenger records quickly without having a full name or a name’s precise spelling”:

One name-matching technique that airlines have used, called Soundex, dates back more than 100 years, to when it was invented to analyze names from the 1890 census. In its simplest form, it takes a name, strips out vowels and assigns codes to somewhat-similar-sounding consonants, such as “c” and “z.”

The result can be bizarre. Hencke and Hamza, for example, have the same code, H520. If there’s a Hamza on the No Fly List, a traveler named Hencke could be pulled aside for a background check before being allowed to board.

A 40-year-old method designed specifically for airlines does something similar, stripping names down to consonants and pulling up names that have the same consonants in the same order. A third technique sometimes used by airlines hunts for matches based on the first few letters of surnames.

Hence Mr. Musarra’s troubles in Juneau. In an algorithm used by Sabre, whose software runs Alaska Airlines’ reservations system and many others, “Musarra” appears to pop up as a match for any name starting with “Mus.” A fair number of names from the Mideast and Central Asia begin that way, including at least one on the No Fly List.

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