United Airlines has added a feature to its mobile app that scans passports and lets passengers check-in for international flights up to 24 hours before departure.
The app uses the device's camera function to take an image of the passport, which is then verified for security.
Once this has been done, the passenger is sent an e-boarding pass, meaning check-in can then be bypassed at the airport.
The process takes roughly two to three minutes.
However, those who require additional travel documentation, such as visas, will still have to go through the traditional check-in process.
Passport scans are stored securely within the app, and can be reused again in the future.
Scott Wilson, United's vice president of merchandising and ecommerce, said: "We are focused on building the most useful travel app in the industry for our customers.
"The new passport scanning feature saves valuable time and provides customers with more options to control their travel experience."
The function is available on both iOS and Android mobile devices.
In June, United installed 20 automated passport control kiosks at Newark Liberty International Airport (see news, June 26).