AN Al-Qaeda suicide plot to hijack several passenger jets simultaneously — including a British Airways flight — and crash them into high-profile American targets has been uncovered by the security services.

The American capital and nuclear power stations on the country’s East Coast are said to have been among the terrorists’ potential targets.

The September 11-style plot explains the grounding of 10 US-bound flights across the world over the seasonal break.

According to a senior intelligence source, an informant tipped off authorities the weekend before Christmas. He claimed that Islamic extremists intended to hijack flights operated by BA, Air France and AeroMexico, the Mexican national carrier.

The informant said that as well as targeting Washington, New York and Los Angeles, the terrorists were planning to launch a strike on an oil terminal in Alaska. A CIA assessment of his information subsequently identified nuclear plants on the eastern coast of America as possible targets.

Detailed security checks were conducted on all US-bound flights operated by the three carriers after the intelligence emerged about the alleged plot. All passenger lists were cross-checked against an FBI watchlist of known terrorist suspects.

As a result, 10 US-bound flights were grounded: two BA flights to Washington, two AeroMexico flights from Mexico City to LA and six Air France flights from Paris to LA. At least three other flights were escorted into American airports by F-16 fighter jets and one Mexican airliner was even forced to turn back in mid-air.

BA also grounded two flights to Riyadh, Saudi Arabia, which were due to fly on New Year’s Eve and yesterday afternoon. It is understood that these cancellations related to separate intelligence.

Although flight 223, BA’s service to Washington, was cleared by British officials for take-off yesterday afternoon after being cancelled for two days running, the United States was still not satisfied, leaving it delayed on the runway for 3½ hours while the 225 passengers were subjected to additional questioning on board.

The aircraft eventually took off at 6.30pm and was due to arrive at Washington Dulles airport at 2.10am today.

Intelligence sources yesterday confirmed that the cancellation of the US-bound services was triggered by information provided by an informant “outside the US”. The warning was of an imminent attack on American soil with Washington, Los Angeles and New York identified as targets.

It is thought that another target was the Alaskan port of Valdez, the terminal for an 800-mile pipeline which carries 17% of America’s domestic oil supply. The informant also named specific routes and flight numbers, including BA223, as part of the hijack plot. It is understood that intercepts of communications between known terrorist suspects also suggested the significant risk of an attack.

On the same weekend that the intelligence was received from the informant, Tom Ridge, the US homeland security secretary, raised the security threat for US citizens to “code orange”, the second highest level. He said that the country faced the risk of a terror strike which “could either rival or exceed” September 11.

All passenger lists on the jets believed to be potential targets were checked. Valdez was put on high alert and the transfer of oil to tankers was suspended. Some passengers listed on Air France flights to LA appeared to match suspects on the terror watchlist and six flights were cancelled on Christmas Eve and Christmas Day. One passenger who had a similar name to a Tunisian terrorist turned out to be a five-year-old child.

French security officials insisted that the decision to ground the planes was taken on the basis of “significant intelligence”. One of the passengers who failed to turn up was a trained pilot from the Middle East who has since disappeared and cannot be traced, according to US intelligence sources.

Checks on the British passenger lists revealed other apparent matches with names on the terror watchlist, but none is thought to have been confirmed.

Spurious matches are not uncommon because of the similarity of many Arabic names. As well as checks on specific aircraft, new security measures were implemented. The British government said last Sunday that armed air marshals would be deployed on US-bound flights where needed.

David Blunkett, the home secretary, wants to hold an urgent meeting of the British and American “contact group”, which contains security and intelligence officials, police and politicians from the two countries.

There are signs of tension between London and Washington over the extent to which Britain follows every command from the United States after terror alerts. “The notion that the US can bounce the rest of us into cancelling flights all the time needs to be addressed,” said one British minister.

Yesterday passengers checking in for BA flight 223 to Washington Dulles airport said that they were not deterred by the security alert surrounding the service.

Ralph Hodgson, 58, a businessman from Newcastle, said: “I’ve absolutely no worries at all about getting on this flight. I think if anything’s going to happen, if your number’s called, then your number’s going to be called.”

In a separate security alert BA’s flight to Riyadh was cancelled for the second time in four days after intelligence reports relating to a potential surface-to-air missile attack on a British carrier.

This weekend government officials were believed to be advising the Saudi authorities on measures to improve ground security at Riyadh airport.

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