Getting from Cusco to La Paz to Sucre?
 

I'm in Cusco and trying to get to La Paz. I think I'd like to fly, but am having a difficult time getting info on flights. There seem to be a few direct flights a week on Aerosur. Anyone know what days every week they fly? Are there any sites other than Aerosur's that I can book tickets on?

Then once I'm in La Paz I'd like to go to Sucre, but have been told the bus is pretty perilous. Are there any flights? Looks like Aerosur sells flights with a mandatory overnight layover in Santa Cruz, which isn't ideal.

Any suggestions would be appreciated!