SOUTH BARRINGTON, Ill. (AP) — Two F-16 fighter jets intercepted a plane flown by a 75-year-old woman after it entered restricted airspace during President Barack Obama's recent visit to Chicago, federal officials said Thursday.

Two F16s intercept wayward plane on 8/4/2011, but couldn't on 9/11/2001?

http://news.yahoo.com/f-16s-intercept-plane-during-obamas-chicago-visit-003735401.html