The Trump administration's drive to use facial recognition technology at US airports for all international passengers has run into opposition from privacy and civil liberties groups.

Under an executive order, the technology - which might allow travellers to board planes using their face as a passport - will be in place at the top 20 US airports – including New York’s JFK, Los Angeles, Boston, Las Vegas and San Francisco – by the end of 2021.

The purpose is to track visitors as they leave the US, checking biometric data of departing passengers against the information collected by the US Department of Homeland Security on arrival.

This will represent a massive expansion of technology already in use at a number of European airports, including London Heathrow. It is anticipated that the system will be used to collect data on more than 100 million passengers leaving the US.

US citizens and green card holders will be able to opt out and have their passports inspected at the gate and their photos will be destroyed within 12 hours. However, it will be compulsory for remaining passengers, and their photos will be retained for up to 14 days.