Betty, if only there were a definitive answer to that question. There're two schools of thought on this: one say every nut job with half a bag of fertiliser and a grudge against the West will be trying to make a point. The other school says security will be tighter than ever with every anti-terrorism force on high alert, scrutiny at airports more intense than ever and millions of ordinary people on the look out (let's roll!).
No one is going to be able to make your decision for you, it's up to you to assess the risk and decide what's right for you.
Arm yourself with some knowledge about identifying terror risks and what to do in the event of an attack with this article: http://journals.worldnomads.com/safetyhub/story/72300/Worldwide/What-to-do-in-a-terror-attack
There'd be very few occasions in the past 10 years when the THREAT of a terror attack has been higher, you'll really need to be on your guard.
I see from another question you've asked you're travelling with a tour group... why don't you ring them and ask what increased security measures they're taking and what their plan is in the event of more trouble? If you're still nervous about going, ask them if they'll let you defer your trip to another time, I'm sure they'd be accommodating.
Phil over 8 years ago