British Airways, has expressed doubts British government plans to have armed marshals on both domestic and international passenger flights.
If the move goes ahead, Britain will join nations including Israel, Germany, the United States and Australia in using onboard armed guards.
British Transport Secretary Alistair Darling said the government, in response to the increased threat following last year's September 11 attacks, decided earlier this year that in-flight security should be increased by placing undercover armed police officers on civil aircraft.
"That capability now exists and is a sensible and measured addition to the range of security measures we have available for addressing the threat to UK interests and to UK aviation," he said in a statement on Thursday.But BA said it was worried about the possibility of guns being fired on its planes.
"We have concern about the presence and use of firearms on our aircraft," a BA spokesman said.
"However, we are working closely with the government to ensure these plans do not jeopardise onboard safety and to ensure that the correct procedures are in place should deployment be necessary."
Darling's officials declined to say whether the government would insist airlines accept the agents or what proportion of flights would be covered.
But Darling's statement left no doubt that the government will press for airlines to accept armed guards.
The image of passenger planes smashing into the World Trade Centre remains seared into the public imagination and passenger plane traffic dropped sharply after the attacks.