A: Tell me, which day can you fly?
B: I haven't decided yet. What's the hurry? We still have time.
A: No, we don't. It's Christmas soon, everyone plans to travel.
The travel agency said we have to book (at least) 5 days before departure otherwise we can't buy air tickets.
we have to book 5 days earlier before departure. - NO
we have to book preir to 5 days before departure. - NEITHER
We must/have to book 5 days before departure.
We must/have to book at least 5 days before we leave.
The booking must/has to be made at least 5 days before departure.
The booking must/has to be made 5 days prior to departure.
earlier-prior to-before -they all have the same meaning and should only be used once in a sentence. earlier doesn't fit in this context.
i hope this was helpful and accurate!
Student or Learner