It was like a mass sell off for a while yesterday, with the FTSE rapidly falling by 100 points. But if there is a terror premium built into shares, and a terrorism plot has been thwarted, you would, if anything, expect shares to move the other way, and eventually, that’s what happened.

In the UK, the FTSE ended the day 37 points down, but in the US, where markets had more time to digest the positive implications of yesterday’s news, the Dow Jones Industrial Average moved up 48 points.

The same principle applies to oil, black gold fell $2 a barrel, after it had spent the last couple of weeks flirting with record highs

Some investors took the opposite approach, with analysts warning that at times of heightened risk, some investors become more risk averse.

But the airline industry really did receive a hit, shares in BA were down 4.9 percent, for example. EasyJet cancelled all flights in and out of London, and saw shares fall 1.8 percent, and Ryanair saw a 2.7 percent share price drop.

After the events of September 11 2001, worldwide air travel fell by a third, and in the aftermath, several airlines went bust.

But in fact it wasn’t just tourism that took a very real knock, any business concerned with exports and imports received a potential set back, with anecdotal evidence suggesting many business people took an about-turn back to their office, cancelling business trips abroad altogether, after they saw the length of queues.

Consultants at Grant Thornton rapidly got their calculators out, and after some number crunching said that the British economy would suffer to the tune of £10 million a day through lost production – which actually when you think about it is quite small, in the scheme of things.

But the question is, how long will the delays last? Antonia Kimberley, a spokeswoman for Heathrow, said: “It is still unclear as to how long these security restrictions will last, but we hope to be operating normally tomorrow.” But for the airline industry it’s another knock, and another reason why some will choose to stay at home.

That the plotting was apparently foiled is good news, but its often human nature to focus on the negative, and no one wants to be reminded on the extent to which we are at risk. And in the mean time, security measures will last for some time, making more delays inevitable, and maybe hitting the airline industry harder still.

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