America foils a plot by al-Qaeda in Yemen to detonate an upgraded version of the failed 2009 "underwear bomb", according to US officials.
The device was seized abroad by intelligence operatives and is now being studied by the FBI in the US.
Reports say no target had been chosen and no plane tickets purchased by the time the alleged plot was foiled.
Officials say there was never any risk to the public. It is not clear what has happened to the would-be bomber.
News of the discovery comes shortly after the first anniversary of the death of Al-Qaeda leader Osama bin Laden.
The device is similar to a bomb sewn into the underwear of a man who tried and failed to set it off over Detroit on Christmas Day 2009.
US officials told the Reuters news agency the device had been seized within the last 10 days.
"As a result of close co-operation with our security and intelligence partners overseas, an improvised explosive device (IED) designed to carry out a terrorist attack has been seized abroad," the FBI said in a statement.
"Initial exploitation indicates that the device is very similar to IEDs that have been used previously by al-Qaeda in the Arabian Peninsula (AQAP) in attempted terrorist attacks, including against aircraft and for targeted assassinations," it added.
It is not clear who built the device, but officials say it shares some features with the bomb sewn into the underwear of would-be suicide bomber Umar Farouk Abdulmutallab.
Abdulmutallab's "underwear bomb" was not detected during security checks at airports in Lagos, Nigeria, and Amsterdam before he boarded Northwest Airlines Flight 253 for Detroit in 2009.
On the flight, the bomb did not detonate fully and passengers had to put out the fire. He has since been sentenced to life in jail.
In a statement, the Department of Homeland Security said air security would continue to incorporate threat and vulnerability analysis, pre-screening and screening of passengers, as well as random searches at airports, air marshals and other unspecified security measures.
It added: "We have no specific, credible information regarding an active terrorist plot against the US at this time, although we continue to monitor efforts by al-Qaeda and its affiliates to carry out terrorist attacks, both in the homeland and abroad."