Is there a way to scan unusual barcodes?
The Bar-coded Boarding Pass (BCBP) code is common for flight tickets. There could be other codes too, but there doesn't seem to be any app for it yet.

Mails also have different codes. The US seems to be using Intelligent Mail barcode (IM barcode). IMb Reader can be used for this.

Bottomline: there are several possibilities for the codes. You need to check first what code an airline or postal service is using. Then, check if there are apps for it.