Think you're safe on a plane? Federal undercover investigators who sneaked prohibited items with alarming ease past Homeland Security Department airport screeners have been smuggling simulated bombs and weapons aboard planes during tests as far back as September 2002.

In a 2007 report, Government Accountability Office auditors said they were able to pass through security checkpoints with parts for several improvised explosive devices with them or in their carry-on luggage.

A 2008 report noted another series of vulnerabilities discovered by TSA dating to 2002. That audit says the agency made 43 recommendations over a five-year period to mitigate security gaps.

And earlier this year, the Homeland Security Department's inspector general revealed that a convicted felon was allowed to use an expedited screening lane.