Yes there’s bidding. But I suppose some want the surety that they won’t get called up for long haul.
no one can have that surety. Every 3 months they have to fly on each family of aircraft they are licensed on. So that’s a least one 777 route every 3 months (I guess they could bid for a MAD) and then probably one of either 747 / 350 / 380 (whichever is their third aircraft type in addition of course to the 320 series which they’d all be licensed on)