(CNN) -- Pilots for UPS charged Monday that their employer is failing to protect them from acts of terrorism.
"Our crew members deserve a reasonable expectation of safety. We believe that current standards in air cargo screening are inadequate," Brian Gaudet, spokesman for the Independent Pilots Association -- the union for UPS pilots -- said.
Since August 1, federal law mandates screening of all cargo aboard passenger flights, but there is no such requirement for flights transporting cargo.
Rep. Edward Markey, D-Massachusetts, announced he would introduce legislation to require complete screening of packages on board freight carriers.
"Air cargo on cargo-only planes is much more vulnerable to being exploited by al Qaeda than cargo on passenger flights," said Markey.
A package containing a hidden explosive device, sent from a UPS office in Yemen and bound for Chicago, was located Friday at England's East Midlands Airport.
UPS adamantly denies it is placing any employees in danger.
"We have a multi-layered approach, we have processes and procedures in place to ensure safety of shipments and our people," said UPS spokeswoman Elizabeth Rasberry, who would not provide details of security measures.
The Cargo Airline Association also argues screening is adequate. "Better intelligence is the answer," said Steven Alterman, president of the association. "And the intelligence worked in this case."