Are stolen passports giving terrorists easy access to international targets?

As the search for the missing Malaysia Airlines Boeing 777 enters its fifth day, questions about what happened to flight 370 center on the underworld of stolen passports.

Earlier this week, Interpol revealed two Iranian men boarded flight 370 using stolen documents. Authorities in Iran later confirmed the men’s identities using a picture taken at the boarding gate in Kuala Lumpur. The report fueled speculation that hijacking might have caused the plane’s mysterious disappearance. But forged documents are a booming business in Malaysia and neighboring Thailand, and authorities said the men were illegal migrants, not terrorists.

Every day, passports are stolen in tourist beach resorts like Phuket, Thailand. After a photo or biometrics makeover, shadowy networks resell them on the black market. A criminal or trafficker may later mine identification information and use the old document to “legitimately” apply for a brand new passport containing his own photo and biometrics, making a “true lie.” Such documents are like gold for those wanting to hide their origins or intentions, or migrate illegally. Ramzi Yousef, mastermind of the first World Trade Center bombing in 1993, used a variety of stolen passport to facilitate his movements.

Technology is available for catching those trying to fly with forged documents, but Interpol Secretary General Ronald Noble said most countries simply don’t use their database to screen international travelers for stolen passports. He called it a “gaping hole” in global security. Already in existence for 10 years, the Stolen and Lost Travel Document (SLTD) international databasecompiles details of the nearly 40 million reported stolen passports so officials can check for criminal use. With 29 million flights worldwide each year, only a fraction of passengers—four out of 10—get checked. Most of the flights that do get checked originate in the United States, the United Kingdom, and the United Arab Emirates.

Last year alone, Interpol estimates another 1 billion passengers’ passports went unchecked. “We still rely on a model … where in far too many countries we wait for threats to reach an airport before trying to identify them as such—when it is just tragically too late,” Noble said.

Such glaring underuse propelled Interpol to make its Lyon, France-based computer system open to private industry, starting with airlines. It hopes later to expand to the travel, banking, and tourism sectors. Customers using a passport to book a flight, check into a hotel room, or even open a bank account would be screened.

Through an instant passport screening program called I-Checkit, airlines will be able query the stolen documents database but will not have direct access to it. Air Arabia and Qatar Airways are two companies now testing the new program. The database contains and matches passport numbers and nationalities, as well as birth dates. But biometric data is not accessible.

International cooperation helps curtail the stolen documents market even as passport forgers use increasingly sophisticated technology and do mass alterations: In Thailand—where the stolen passports used on flight 370 were taken—immigration police last year caught a Thai national with 5,000 fake passports.

But it’s not all bad news. In 2012, the Interpol SLTD database identified 60,000 stolen documents.

The Associated Press contributed to this report.