But preprinted tags, manually read by baggage handlers, couldn't cope with the world's ever-growing volume of passengers and bags, let alone the increase in connecting flights with ever-shorter connecting times at ever-bigger and busier airports. The solution was the ABT's combination of two features: custom printing and a bar code.
Just as you can track, step-by-step, a package you've sent by FedEx, airlines use bar-coded tags to sort and track bags automatically, through the airport, and across the world. That's a huge change from the old days, when bags were dropped into the "black box" of a manually sorted baggage system. But crucially, an ABT doesn't just contain a bar code — it's also custom-printed with your name, flight details, and destination. That made the global implementation of ABTs much easier, because early-adopters could introduce them long before every airport was ready — a huge advantage when it comes to seamlessly connecting the world's least and most advanced airports. And of course, ABTs can still be read manually when systems break down.
While bar codes have changed many industries, aviation has made special use of them. For example, bar codes reduce delays by computerizing the task of ensuring that every bag that's loaded on a plane is matched to a passenger who's actually boarded — an important security measure. And rough-and-tumble baggage systems present a much more challenging and three-dimensional environment than, say, a supermarket checkout. So note how the ABT's bar code makes two appearances on the tag, offset by 90 degrees. It's a small tweak that greatly improves readability by automatic and hand-held scanners.
Note, too, the small extra labels that each bear a copy of the bar code. Technically known as bingo tags, removable stubs, or stubbies, these were originally detached to help airlines track which bags were loaded. These days they're often placed on your bag as another safeguard against a detached tag. (Ironically, stubbies from your previous flight can confuse airport scanners on your next flight — be sure to remove them after each trip.)