Europe had terrorist incidents involving planes long before 9/11. As a consequence air travel (domestic or international) had greater security checks but nowhere near the level we see now in America.
Here is the problem, no amount of security checks can guarantee that there will not be a terrorist incident on a plane.
Even accounting for 9/11, other terrorist incidents on airplanes and plane crashes, the likelihood of you being killed in one is very small.
But the politicians are faced with a decision, respect civil liberties and relax security to common sense levels or ratchet up security to ridiculous levels. If they do the first and a terrorist attack occurs they will get the blame.
Ultimately it is a risk problem, and it is the voters that need to tell those in charge that they understand the risk and won't blame the government for "not protecting them" if something bad happens to them.