I'd have thought that post 9/11, a country which is home to one of the tallest buildings in the world would always be nervous about an incoming unidentified target.
but it wasn't an unidentified track. It was an identified Friendly track which turned round - and if the operator didn't know it's flight plan why would he assume it wasn't planned to?
To mangle a quote frm the FI war - they watched it all the way out and they watched all the way back in again.