Undercover armed police may travel on British passenger flights to prevent hijackings.

Home Secretary David Blunkett and Transport Secretary Alistair Darling are considering proposals to place "sky marshals" on most planes, the government confirmed.

But the proposals have greeted with caution by airlines, who stressed that having guns on planes could pose more of a risk than the initial threat.

What if they are over-powered, what if they fall in the wrong hands?

Stelios Haji-Ioannou easyJet founder

The sky marshals idea was one of the recommendations in a report by former Conservative minister Sir John Wheeler.

There has been sporadic support for the idea of plain clothes armed guards since the 11 September attacks.

But easyJet founder Stelios Haji-Ioannou condemned the plan and said it was better to rely on passengers and crew to overpower hijackers.

He told BBC One's Breakfast with Frost: "I am a bit worried about guns on planes. It's the last place you want guns.

"What if they are over-powered, what if they fall in the wrong hands?"

Safety implications

Critics of the idea of sky marshals have also suggested regular marshals flying on numerous flights would soon be identified by potential hijackers.

Apart from safety implications, airlines will also be concerned about the cost of a scheme while they are negotiating troubled times financially.

But Liberal Democrat transport spokesman Don Foster backed the idea, saying: "This is a welcome proposal that has the potential to reduce any terrorist threat and reassure passengers.

EasyJet's founder is against the proposals

"It must be done in conjunction with the airlines, and with their full support."

British Airways says it has work to do with the government before any guards could be put on planes.

A spokeswoman said: "If armed police officers were to be introduced on UK aircraft by the government, we would need complete confidence that it would not compromise the overall safety of the aircraft.

"Clearly as a responsible airline we have concerns about the use of firearms on board our aircraft."

No mention

Virgin was equally equivocal, with a spokesman saying: "Since 11 September, our focus has been on two areas - strengthening and protecting the security of the flight deck and enhancing the screening and profiling of passengers and baggage."

A summary of Sir John's report was published last month and made no mention of the idea of "sky marshals".

A similar scheme in Australia costs �50m a year.

A Home Office spokeswoman said: "The idea of sky marshals is one of the recommendations of the Wheeler report. Whilst it is an option, no decision has been taken on it yet."