Who lost my lap infant? My attempt to reverse engineer a decade-long airline bug

Hello, I'm the author! On our first cross-Atlantic trip as a family, United Airlines failed to issue my baby daughter a ticket. Then on the way back, Lufthansa lost all track of her on the reservation.

As a software engineer with an interest in legacy systems, I couldn’t resist trying to reverse engineer the bug. I came up with a theory, and along the way uncovered some fascinating aspects of the international messaging standard — it turns out that in the reservation data model, lap infants are modeled as a “special service request” (`SSR INFT`) rather than a full passenger. This is the same field used for vegetarian meals (`SSR VLML`) and bulky sports equipment (`SSR SPEQ`).

I’ve never worked at an airline or in the aviation industry more broadly. I pulled together this investigation from public sources. If you work in aviation, I’d love to hear from you! What is the real issue?

I would call this a feature, not a bug.