Unlike previous attacks, airline shares did not dip significantly after the security alerts, with Ryanair shares actually rising four cent to 4.99 and British Airways stocks jumping from �4.18 on Monday to �4.40 on Wednesday.

Neil Glynn, an aviation analyst with NCB Stockbrokers, said it was becoming clear that the market may be starting to factor in the risk of terrorism attacks in its calculations regarding airline stocks.

"I would say that investors are prepared to see this kind of occurrence from time to time. These kinds of events have occurred periodically and there is no indication that it will go away in the near future, " he said.

"This industry is volatile and we have terrorism and other external effects. There are a lot of factors impacting on prices besides terrorism. Yields are big area of focus at the moment."

Meanwhile, global financial services giant Citigroup has also indicated it believes that the terrorism alerts will have little impact on European airlines. Earlier this week, one of its reports identified that the "hassle factor" was a bigger threat to airlines than terrorism.

"The worst outcome for the airlines is if additional airport security checks increase queuing/waiting times beyond already stretched levels and these are broadcast on TV. These could deter discretionary leisure traffic, " it said.

Irish airlines have indicated that the failed attacks have had little impact on their businesses. A spokesman for Ryanair said things were "pretty much the same as before" and that queuing at British airports didn't seem to have become worse.

A spokeswoman for Aer Lingus said that "the security alert at Glasgow airport last weekend and the incident at London Heathrow on Monday have led to no visible down turn in Aer Lingus bookings".

Aer Lingus shares finished the week at 2.54, down 4.5 per cent over the week since the Glasgow incident.

Ryanair was up 4.6 per cent and BA was up more than 3 per cent over the week.