and mabybe a "ordinance dropped/fired (for rockets) so you can time how long it takes from drop to boom.
Then with enough practice, you will know how long it takes for the bomb to hit from 30,000/25,000 etc... So later if you have a mission and you want crap to be blown up at say 1600 on the dot, you know when you need to be over target to acheive the goal.
Seems like a lot, but its really not.