Currently, Treasury has no requirements for airline tickets to be bought in advance, leaving senior advisers all the time they need to book the ticket. Yet we also simultaneously require refundable tickets - meaning that if there were any changes, the ticket could be switched.
We would thus be much better off if we required people to book their tickets at least two weeks ahead, and using the "refundable" status of the ticket to change or cancel (and pay extra charges) as needed. If the trips go as planned, we won't need to change and will save on the price of the ticket. If not, at least we're using the "refundable, changeable" part of the ticket that we're paying those big extra $ for.