The world is awash in stolen passports such as those that two passengers used to board the Malaysia Airlines flight that disappeared Saturday, but only a few countries closely monitor their use.
More than 40 million travel documents, mostly passports, have been reported stolen, according to a database begun in 2002 -- following the Sept. 11 terrorist attacks on the United States -- by the France-based international law enforcement organization Interpol.
"Only a handful of countries worldwide are taking care to make sure that persons possessing stolen passports are not boarding international flights," Interpol Secretary General Ronald Noble said Sunday. His organization confirmed that at least two stolen passports were used to board to missing flight MH 370, which lost contact with air traffic control shortly after leaving Malaysia's capital, Kuala Lumpur.
Interpol said no country has made any checks on those passports since they were reported stolen in Thailand -- an Austrian one in 2012 and an Italian one in 2013, adding it's unable to say how many other times they might have been used.
"It is too soon to speculate about any connection between these stolen passports and the missing plane," Noble said. Yet he said their use is a "great concern' and should prompt countries and airlines to check Interpol's data before allowing passengers to board.
The United States uses Interpol's database, which started with a few thousand records, more than any other nation to screen the background of people entering the country. It does more than 250 million checks a year, followed by the United Kingdom with at least 120 million checks and the United Arab Emirates with at least 50 million.
Interpol makes its database available to all 190 member countries but cannot force them to integrate it into their own systems, according to Interpol's press office, which declined to name which countries -- other than the U.S., the U.K. and the UAE -- have done so.
Last year, Interpol reports, passengers boarded planes more than a billion times without having their passports screened against its Stolen and Lost Travel Documents database.
The data are currently accessible only to law enforcement, but Interpol is looking at an "I-checkit" pilot project that would extend availability to the travel, hotel and banking industries.
Fake passports, often obtained on the black market, have been used before by terrorists, including Ramzi Yousef, convicted of carrying out the 1993 World Trade Center bombing in New York.
The 9/11 Commission report. issued in 2004, detailed how the 9/11 hijackers obtained and modified the passports that got them into the United States. It lists five ways terrorists can use passports, including changing stolen ones with new photos or doctoring them to create a fake travel history by adding or removing visa entry stamps.
Since that report, passport security hasn't improved much, mostly because i'ts not been exploited in a recent U.S. attack, said Michael Greenberg,a former Clinton administration official and founder and director of the University of Maryland Center for Health and Homeland Security.
"Passports are a very weak link in the security system," he said, noting there's still no effective way to ensure that the person presenting a passport is the person to whom it was issued. He says they're easy to steal, replicate and adulterate, and international fliers not leaving from or arriving at a U.S. airport face a different system from the one used by the United States.
Despite the 9/11 report's discussion of biometric passports – virtually impossible to replicate and intrinsically linked to whoever it was issued – "the federal government keeps the system we have in place and hopes nothing bad happens," Greenberg said.
Still, he said the U.S. system, which involves checking reported stolen or false passports against its own watchlist, is better than the one used internationally. Had the Malaysia Airlines flight been headed to the United States, he said, the passenger manifest would have been checked before takeoff, primarily against the U.S. watchlist rather than Interpol's database.
Many nations, he said, neither maintain their own watchlists nor check any list as carefully as the U.S. "So if you're flying between two foreign airports, you're at the mercy of whatever the host and receiving countries are doing,' Greenberg said.