Ianto knows much better than Jack where the archives are clear for landing or not, so he doesn't volunteer a suggestion for that.
"Yeeeahhh..." That time before he ran off with the TARDIS, and the more recent tampering, and hell, their own messing about with it to give the Doctor and Donna that signal... "It's gone through a lot of tampering in the past couple years. No, make that several! Almost forgot Blon doing it, too!"