It turns out that legacy systems are often interesting when you look at them. There’s an interesting summary of the various numbers you’d find on a boarding pass here.

The e-ticket system is an outgrowth of SABRE. There’s a whole system of locator numbers (six alphabetical characters, such as IXYDBY). There are a number of other related and interesting concepts, such as the Passenger Name Record.

What I want to share are some details about the document or e-ticket numbers. Sometimes these are relatively hidden. With American Airlines, you’ll see these in your booking emails, and I would imagine they are encoded in the barcodes used on boarding passes.

On American Airlines, a seat upgrade might look something like this: 001 0629 793337 (spaces added).

Let’s break it down:

• 001 is the airline code, in this case for American Airlines. I’m supposing that more generically, this might be called a provider code or carrier code– I think it’s possible to have train or other transit providers.
• 0629 is the form code.
• 793337 is the serial number; the specific document in question.

A ticket looks like this: 001 2280 476034. Note that the form code has the form 2XXX.

At least for American, a few examples of form codes:

• 0XXX are add-ons
  • 02XX checked bags
  • 04XX same-day upgrades
  • 06XX seat upgrades (eg 0635)
• 2XXX are tickets
• 7XXX are third-party tickets, such as those booked through Costco Travel or Expedia

As an aside, the AA refunds request site needs these e-ticket numbers to request refunds.