The letter and number codes on a boarding pass tell a lot about you, including whether you've been chosen for extra screening ...

Flyers are warned to avoid uploading photos of boarding passes online - or even discarding of them in public bins - as the PNR can give hackers a deep insight into your travel plans and habits.

Passenger Name Record (PNR) More commonly known as a booking reference or reservation number, a Passenger Name Record (PNR) is a six-digit alphanumeric code that appears on every boarding pass.

The letter and number codes on a boarding pass tell a lot about you, including whether you've been chosen for extra screening. Here's what they mean.