Originally Posted by
barelyelite
Never checked in online before?!
The bottom portion is for your records. Technically, they can keep the top portion upon you boarding the aircraft, though I've never had this happen. I typically fold the sheet in half and present it that way upon boarding. IME, this is what most others do as well.
I've had several instances where the scanner at the gate was not working properly and they kept the top half. I did get credit for flying--they
manually entered the info into the computer.