Biometric passenger checks have been launched at Heathrow that will allow domestic travellers to access more shops and restaurants.
Travellers waiting to board UK-bound flights will now be able to access the larger international departure lounge at Terminal 1, providing they are willing to undergo the biometric checks.
Passengers will have to provide four fingerprints and have their photograph taken at security so it can be used to check their identity at the gate.
The technology ensures that a transferring international passenger cannot swap travel documents with a domestic passenger in order to evade immigration control.
Fliers connecting onto a UK domestic flight will be directed to follow the international route but will be able to refuse to provide the fingerprints and go to the domestic departure lounge instead.
A spokeswoman for BAA said: "It allows domestic passengers to take advantage of the larger international lounge."
Biometric data is already in use for border-control purposes at other airports in the UK, including Gatwick and Manchester Airport.
The system will also be used at Heathrow's world-class Terminal 5, when it opens next month.
British Airways, BMI and Aer Lingus all offer domestic flights from Terminal 1.
The personal data is encrypted immediately and is destroyed within 24 hours of use, in accordance with the UK Data Protection Act.