The bar codes on paper or electronic boarding passes contain a good deal of data about a given flight. One of my goals for Flight Historian is to allow me to add a new flight by scanning the bar code, but in order to do that, I need to write a Ruby parser for the data in these boarding passes. This parser will accept bar code data, and return a collection of field names, values, and its interpretation of what those values mean.
One of the more difficult challenges I’m running into, though, is interpreting the date of the flight from the bar code.
One of the minor features I’ve added to the flight log is country flags for tail numbers. Every aircraft is registered to one country, and each country has its own assigned format for tail numbers, so it’s possible to look at each tail number and determine what country it’s from.
Since this operation is matching a string to a pattern, it made sense to create regular expressions for each country. For most countries, whose tail number is a unique prefix followed by a dash and three or four letters, this was easy to do. But the United States rules for valid tail numbers are substantially more complicated.