OK, I think one important distinction here needs to be made - if travel is client facing and especially - if it is client billed.
In our Travel Policy and Concur system there is special designation for these - CF (Client Facing/billed) and NFC respectively. Client billed flights have much more flexibility to the point that one can decide which flight to book and which class.
NCF cases are most restricted - the travel is not related to client meetings and/or revenue - cheapest Y for everybody except board members - they can book J if flight is more than 4 hours.