Strict new immigration rules for the United States are catching up with people arriving in the country without biometric passports.
Since the 01 April all people arriving in the US, regardless of whether it is to live, work or for a holiday, must have a biometric or e-passport to enter.
But millions of people with older passports that are due for renewal but still valid for travel are getting caught out.
The problem has been highlighted in the UK where officials say that millions of British citizens would not be granted entry even though they have a valid passport and some have already found themselves barred.
The media has reported that people are arriving to check in for flights and being turned back at the check-in desk at the airport. It is particularly affecting people with British passports because currently British citizens do not need a visa to travel to the US, just a passport that is valid for at least six months.
E-passports have been around in the UK since 2006 but millions still have the old style passports which do not have a digital chip containing biometric information that can be scanned and read.
Under the rules British citizens travelling on the visa waiver scheme must have a passport that contains the necessary electronic information.
“People looking to travel under the Visa Waiver Program must possess passports with specified security features. These features are that the document must be an electronic passport with a digital chip containing biometric information about the passport owner and must also have a machine readable area of the biographic page,” said a US Homeland Security spokesman.
“E-passports are issued by the proper passport issuing authority and must meet international standards for securing and storing information corresponding to the passport and traveller,” the spokesman added.