Hey guys. I've been reading how to see if there are seats available or not but I cannot find the way of doing it. You guys helped me a lot with other information but now I would be so happy if you help me to know if there are seats available on this flight:

17 March 15:35 CAG (cagliari) to BCN (barcelona)

return

20 March 13:25 BCN (barcelona) to CAG (cagliari)

The fact is that is my mothers 50 birthday and those flights are expensive so I asked a friend that works in vueling and told me she can buy "awaiting tickets" which if the flight is not full you can fly.

I would like to know if to pick these tickets or to buy them for lot of money.

Thank you guys,

Alex