Aviation expert David Learmont says having armed guards on board flights is going to be "pointless".
Mr Learmont says passengers would overwhelm hijackers
Air marshals are due to start flying on routes to the US this week in a move which has been attacked by British pilots.
Mr Learmont, of Flight International magazine, said if would-be hijackers were able to get a gun on board, it would be a handgun.
"You couldn't get a Kalashnikov on board, it's so big that even the doziest guy on the x-ray machine in the airport would see that being got on board.
So we're talking handguns."
He said that all flights into America had re-enforced bullet proof cockpit doors which stay locked during the flight.
"Nobody can get into the cockpit and take the aircraft over so all that can happen, and this is the worst, is that one person with one handgun can get on board and threaten one passenger," he told BBC News.
"By the time that he might have harmed that passenger he'll be under a heap of other passengers just like the shoe bomber was a year ago.
"When people see suspicious things happening on an aircraft the passengers are no longer passive."
He said the strong cockpit doors were the reason the airlines and the International Air Transport Association, the trade association of all the world's airlines, were opposed to introducing air marshals.
"The reaction of the pilots' union, has been we don't want more guns on board an aircraft.
"If somebody does manage to smuggle a handgun on board, we don't want gun fight at the OK Corral going on in the back of our aircraft."
He continued: "So you don't need security guards on board any longer - at least not ones that are armed with firearms.
"That just increases the danger to the passengers on board and this, I think, is the pointless aspect that both the pilots and the airlines are talking about."
Mr Learmont said he believed the government was a "political statement" which would fail to reassure passengers.
However he said he thought it might deter would-be hijackers.
"If it has a deterrent effect then it hasn't been an entire waste of time."