The UK government has said a parcel found in a cargo plane destined for the US was a bomb.
The device originating from Yemen was intercepted on a UPS flight at East Midlands airport.
British Home Secretary Theresa May confirmed the explosive package could have worked.
“I can confirm the device was viable and could have exploded. The target may have been an aircraft and had it detonated the aircraft could have been brought down,’‘ May said.
The device found in the UK was one of two hidden inside ink cartridges. The other, was discovered in the Middle East, by police in Dubai.
The discoveries have sparked a global terror alert with security forces in Yemen already arresting 26 suspects in connection with the alleged plot.
Both the UK and Dubai parcels were addressed to Jewish targets in Chicago, however the finds also prompted security checks at several north American airports.
US authorities say the potentially deadly devices bear all the hallmarks of al Qaeda. Only last Christmas, the group failed in its attempt to blow up a plane on its way to Detroit.