Just across on CNN International.

Al Qaeda, do you think, or our new friends the Shiites?

Or maybe the Presbyterians?

Standby.

Update: Freedom Folks tips me to the news breaking at the Beeb:

It is thought the plan was to detonate explosive devices smuggled on aircraft in hand luggage, with flights from the UK to the US being targeted.

During the night, police arrested a number of people in London after a counter-terrorist operation they said had lasted several months.

Security at all airports in the UK has been tightened and delays are expected…

“This is a major operation which inevitably will be lengthy and complex.”

After Jean Charles de Menezes and the chemical-vest fiasco, they sure as shinola had better not screw this one up.

Update: CNN quotes Scotland Yard as saying the targeted flight(s) was likely destined for the U.S.

Update: MI5 has raised its threat assessment from “severe” to “critical,” the highest level.

Update: No wonder:

Sky News has been told the plan was to hit around a dozen planes over UK and US cities.

Police are said to have arrested 20 people in London – the culmination of a major covert counter-terrorist operation lasting several months…

Sky News’ Crime Correspondent Martin Brunt said he understood the threat was imminent and those arrested were mainly young, British-born Asian men.

“Asian” is used in Britain to refer to people from the subcontinent. Like Pakistanis.

Update: The Beeb says they’ve arrested “about 18 people.” Carry-on luggage has been suspended on all UK flights.

Update: Sky News has a list of items that Britons will still be allowed to carry on. It’s a short list.

Update: The Blotter had a scoop earlier today about a tip they got from Pakistani intel re: Matiur Rehman, the keeper of the “Directory of Jihad”(?) containing the names of thousands of jihadis who trained in the country’s terror camps. Any connection to this plot? Quote: “U.S. law enforcement officials tell ABC News there has been great concern since last March about a “Pakistani” network that could attempt multiple international attacks.”

Update: Ace is trumpeting this as a possible victory for the Patriot Act and U.S. intelligence, specifically vis-a-vis the flight to Boston two days ago that was forced to return to the UK. Could be, but the British claim the operation has been in the works for months; they were within 48 hours of making a collar when that flight got turned around, so presumably they already had their ducks pretty much in a row. Which means the guy on that flight who showed up on the U.S. no-fly list either (a) wasn’t involved in this or (b) was involved in this, but nonetheless somehow managed to board a plane on its way to America in the midst of a massive counterterror sting. (a) seems likelier than (b), but we’ll see.

Update (Ian @ 4:52am): US raises security threat level to “severe”.

British Airways has canceled all it’s shorthaul flights to and from Heathrow.

25 people have been arrested in connection to terrorist plot, according to Scotland Yard.

Update (Ian @ 5:18am): Metro Police official: “put simply this was intended to be mass murder on an unimaginable scale.”

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Update: Bad morning for me to get a late start, but here we go. TSA has banned all liquid carry-ons in the U.S. except, it appears, baby formula and insulin. A friend of mine once told me that a particular concern of TSA’s is terrorists trying to smuggle C-4 onboard in shampoo containers, because the chemical signature is somehow similar enough to shampoo that the detection equipment doesn’t pick it up. Keep an eye out for details about which explosive these guys were planning to use.

Update: Fox breaks in to say the feds are putting extra marshals on all U.S. flights. 21 people have been arrested thus far in the U.K. I’m hearing now that the plot targeted six flights, not 12 as Sky News had originally reported, but I’ll try to find a source on that.

Update: SeeDubya questions the timing:

Anyone want to bet a beer that this was going down on the Eleventh?

Update: Maybe the question should be, which eleventh?

Chertoff said the plotters were in the final stages of planning. “We were really getting quite close to the execution phase,” he said, adding that it was unclear if the plot was linked to the upcoming fifth anniversary of the Sept. 11 terror attacks.

A senior U.S. counterterrorism official said authorities believe dozens of people — possibly as many as 50 — were involved in the plot. The official spoke on condition of anonymity because of the sensitivity of the situation.

The plan involved airline passengers hiding masked explosives in carry-on luggage, the official said. “They were not yet sitting on an airplane,” but were very close to traveling, the official said, calling the plot “the real deal.”

DHS has raised the U.S. terror alert level to red for flights leaving for Britain. First time we’ve ever gone crimson.

Update: Debbie Schlussel is hearing from her sources in law enforcement that the London suspects are linked to Islamic Jihad. Although there are about half a dozen “Islamic Jihads” from what I understand, so I don’t know how much that limits it down.

Update: Re: the C-4 theory earlier, sounds like the plot was even more clever than that. They were going to build the bombs onboard:

Homeland Security Secretary Michael Chertoff said the restrictions reflected the belief of investigators that the plotters planned to bring liquids on board, “each one of which would be benign, but mixed together could be used to create a bomb.’’

Update: Another lead on the explosives from the Times of London via our affiliate, Flip:

A prime candidate for this would be triacetone triperoxide (TATP), the explosive used by the July 7 bombers. Its two raw ingredients are both liquids, which could potentially be carried on board in sufficient quantities in containers such as bottles of shampoo or contact lens solution.

These could then be mixed in a toilet to make TATP, which is a crystalline white powder. The problem here is that the solid has to be dried before it becomes a reliable explosive. It can also be difficult to detonate, as attested by the failure of the attempted suicide attacks on London on July 21 last year.

The need to get detonators through airport security would also increase the chances of detection.

The problems of assembling and then detonating an improvised bomb of this sort in an airline toilet could explain why the terrorists targeted so many aircraft. It is likely that many of the devices would have failed, so attacking 10 flights would have greatly increased the chances of blowing up one or two.

Nitroglycerin is named as another prime possibility.

Update: Sky’s now saying “at least six airliners” were targeted. The Beeb says “as many as 10.” According to U.S. sources, they belonged to Continental, United, and American Airlines. British police believe the “main players” are all in custody but they’re not sure they’ve rolled up all the co-conspirators yet.

Update: According to a Fox alert, Pakistani intelligence helped foil the plot. Whether that’s actually true or nonsense cooked up to defuse “tensions” between British-born Pakistanis and the rest of the population I leave to you to decide.

Update: People are e-mailing me about reports of an attempted hijacking on a flight between Amman, Jordan, and Qatar. Details are sketchy right now, but it sounds like there was one guy who stormed the cockpit and was subdued. Given how sophisticated the UK plot is, it doesn’t sound like it’s related. Update to the update: They’re not even sure it was a hijack attempt.

Update: Everyone else has mentioned the similarities with the Bojinka plot, so why not me?

Update: Bloomberg said at a press conference that at least one flight was destined for NYC.

Update: Fox reports, to the surprise of no one, that U.S. intelligence has been “working closely” with the Brits on this matter and that, according to Michael Chertoff, the 11 (now 8) missing Egyptian students aren’t connected. Supposedly Fox also reported that Tony Blair warned Bush not to let his little leak problem jeopardize an investigation as important as this one. I can’t find anything about it on the Fox website, but the Conservative Voice swears it’s true.

I doubt we’ll find out whether any extra precautions were taking to safeguard this investigation from certain segments of our intel community. But it wouldn’t shock me.

Update: Bush is speaking right now, and calls the cooperation between the UK and the U.S., and within our own intelligence community, “excellent.”

Update: Lots going on at the Blotter, which notes, again to the surprise of no one, that the suspects are Pakistani. Quote:

Authorities are concerned that those still at large may well have instructions to act now if the plot was disrupted, and they have not ruled out other cities and airports as possible targets of attacks.

They claim that at least nine flights were targeted in three waves of three, waiting an hour between each wave. More nuggets:

ABC News has learned that two “significant arrests” in Pakistan in recent days may have significantly accelerated the pace of the investigation…

British authorities had been tracking some of the suspects for several weeks but stepped in to round up the plotters when they began to book flight reservations.

British authorities have shared parts of the investigation with the FBI, and out of concern for leaks, only the barest details were shared with regional authorities as late as last night.

Update: Bob Owens comments below that whatever the explosive is, it ain’t TATP:

Um, the Times source above doesn’t know jack about TATP. It is extremely unstable, and can go off just by bumping it. It is also not real easy to get the batch “just right”, which is why the second set of London bombs fizzled, and it is doubtful it could readily be made on a plane.

Update: Now here’s something interesting, via a tip. The Scotsman ran a piece two weeks ago on the fact that Muslim business travelers were avoiding Glasgow Airport in favor of Heathrow and Manchester because the profiling at Glasgow was particularly, er, vigorous. I’ll keep an eye out for details about which airports the jihadis were planning to use. No doubt they cased these joints beforehand, and no doubt either that word gets around in the community about which spots are “friendlier” to Muslims than others.

Update: I neglected to mention: Bush didn’t call it a “war on terror” during his press conference. He called it something else.

Update: More on that attempted Qatar hijacking, if it was in fact a hijacking. The suspect is Eritrean, and was carrying a box containing an unknown substance.

Update: Super: “Such mundane items as nail polish remover, disinfectants and hair coloring contain chemicals can be combined to make an explosion and are not detectable by ‘sniffing’ machines, which detect plastic explosives but are not used with all baggage.”

More from Time:

Liquid explosives also attack airline security’s weakest point — the Transportation Security Administration screeners. They are the burger-flippers of the entire security system, and the chances of even the best of them visually identifying a liquid explosive in an innocuous bottle are slim — that’s why Israel’s Ben Gurion airport has a laboratory in the basement to conduct instant tests of liquids found on suspect passengers. If the U.S. system lacks sufficient technology to detect liquid explosives, and if it relies on the TSA screeners to ID possible terrorists, it is, at best, a wire mesh fence.

Time says a guy at National Airport in Washington told them he was able to carry toothpaste and lotion in his hand luggage without anyone realizing.

Update: Video of Bush’s press conference on the plot is here.