sentences:  A spokesperson for CASA, Peter Gibson, told the media that "Tigerair has not been able to, at this stage, convince us that they can continue operations safely, so that's why they're on the ground".Citing a view that future problems would also occur, he also commented that "We [CASA] believe this is symptomatic of problems within the airline [and] we've put them on the ground while we consider all these issues".Tigerair stated that it was co-operating fully with CASA.