Nothing was ready on Air's opening day - believe me!
Scaffolding towers were being removed minutes before guests arrived in Forbidden Valley - even bin-liners were only being put into the queueline bins less than half an hour in advance.
This was, of course, a project expertly managed by Alton Towers over a 2yr period.
Oblivion - 1998 - opened on time, but with hideous reliability problems in first year.
Air - 2002 - opened on time, but with hideous reliability problems in first year.
Rita - 2006 - opened in time (I think), but 1 train only. 2nd train took a while to follow.
Smiler - 2013 - opened well later than planned due to "a bad Winter" [the park started construction too late - anyone with a brain could work this out].
Wicker Man - 2018 - will let the park off a bit here, as the ride was ready, but the weather was horrendous on opening weekend. It did have reliability issues at first too.
When it comes to opening new rides on time & keeping them running reliably - particularly in that all important first season - Alton's history is certainly best described as chequered.