Right now people are processed at the airport first comes first serve no matter what. This problem is made worse by the fact that there is a strong financial motivation to air on the side of caution. When you think about it, every person in front of you with a later departure time is wasting both their time and yours. Until now, getting everyone in the airport to be sorted by departure time was more effort than it seemed worth. While hypothetically you could gain a lot of efficiency, the practicalities of sorting people manually outweighed the benefits.
My solution is to use smart watches to put everyone on a priority queue sorted by departure time. Instead of standing in a line, your watch simple has a number showing how many people are in front of you. This idea combines elegantly simple UI design with proven math!