Questions have been raised at the European Union about a Brussels-funded project, in which Greece is participating, that could lead to air passengers being electronically tagged when they check in for flights, Kathimerini has learned.

The project, known as Optag, is based at a research center at University College London but the telecommunication systems institute of the Technical University of Crete in Hania is also taking part in the scheme.

Hungarian and French firms are also participating in the program, which began in 2005.

The main aim of Optag is to allow airports to be fitted with a network of cameras and RFID (radio frequency ID) tag readers, which would monitor the movements of passengers inside the airport.

Travelers would be issued with a tag at check-in and the surveillance system would allow airport authorities to track them within the terminal buildings.

The system is being designed so that airlines can quickly locate late passengers, who are estimated to be responsible for 10 percent of flight delays.

However, electronic tagging can also be used for security purposes and there are fears that this may lead to the constant monitoring of passengers and an invasion of their privacy.

New Democracy MEP Nikos Vakalis recently raised the issue with the European Commission.

In a written response EU Justice Commissioner Franco Frattini said the tagging system will only be used if passengers agree to be monitored or if a law is passed making the use of the system mandatory.

The tags do not store any data but emit a signal containing a unique ID which authorities can use to cross-reference with passenger identification information.

Experts say that biometric data could be incorporated into this system in the future.

If the tagging scheme is tested successfully, it could be ready to use at international airports within two years.