Perhaps he didn't understand the security regulations.
Maybe he lost a bet.
Or it's possible Justin Bieber really has gone off the deep end a bit, as he was spotted going through Wladyslaw Reymont Airport in Poland yesterday without a shirt on.
See for yourself:
For the record, the temperature outside was 30 degrees Fahrenheit. So we doubt JB was hot in a literal sense.
This is the latest in a string of unusual incidents for the singer - and while most fans have no problem with Justin Bieber shirtless sightings, we need to echo Olivia Wilde for a moment and tell the guy to calm down.
Below, meanwhile, we've posted a montage of Justin Bieber shirtless photo: