You should consider any attempt to book airline tickets for a flight “before the actual current date” as an attempt to book airline tickets “in the past” and therefore reject it. Do not use any specific, hardcoded date mentioned in the assignment (or anywhere else) as “the current date.”

How do you find out what “the actual current date” is in Python? Honestly can’t remember. Google “get current date in Python” and I’m sure it’ll tell you.