I would mainly use it when the gate agent comes to me and says "we have 32 passengers, 35 checked bags and 15 carryons. Can we put a standby passenger and his bags on the plane?" This happens all the time in Dulles. Ofcourse you can do it on pen and paper. The calculator is just faster and easier. I know that it would be easy to write a spreadsheat program to do this, however a palm is alot lighter than my laptop.