While the number of attacks on aviation shows a welcome decrease, it remains a tempting target for terrorists. The reasons stay the same, although the modern world provides extra incentives.  It remains true that an attack on civil aviation gives the terrorist a significant tactical gain for a small cost. 

An incident at an airport or with a plane attracts immediate worldwide attention. The terrorists know this. They can thus garner vast amounts of publicity for their objectives. Helping them is the ubiquitous mobile phone. Linked to social networks, these provide a direct feed to the mainstream newsroom. Traditional media organisations no longer need reporters or film crews on the ground. After all, the public generates the content. Thus, the terrorist attracts instant coverage. 

Meanwhile, the authorities can’t command the spread of news. Even if they can control the traditional channels, it's pointless. Facebook, Instagram and Twitter, amongst others, will pass the message. 

This instant 24/7 rolling-coverage feeds a sense of risk when travelling through airports. The relative hazard to life of terrorism as against other causes is small. Public perception is different. In 2015 in the United States  44 people died due to terrorist acts. The same year 35,398 people die in motor vehicle accidents. Nonetheless, ordinary citizens perceive terrorism as a higher risk.

So, although terrorism poses a lesser danger compared with other risks, it creates a disproportionate sense of unease. The bad guys exploit that. 

The use of terrorist tactics against civil aviation has other benefits. It allows the perpetrators to hit a specific target anywhere on the planet. If you have a beef with the English, attacking a British Airways plane in Asia fulfils your objectives. Then economic consequences can arise, as fear drives passengers away. The Lockerbie attack of December 1988 in part hastened Pan Am's demise. Likewise, regions and resorts can see a significant drop in visitors in the immediate aftermath of an incident. 

Over the years, the actual targets within the civil aviation domain have shifted. In the 1960s we saw hijackings with hostage-taking. That formed the first tranche of modern day terrorism. Later came the bombings of planes by various means.  Then the aircraft themselves used as the weapon as on 9/11. Currently, airports themselves and their infrastructure appear to be the favoured target. But, the indiscriminate nature of terrorism means any or all these options are possible. 

As security for aircraft increased, the terrorists couldn’t get at these potential targets. Yet, they can still access public areas such as check-in counters and arrival halls.

These places see assemblies of people. Gathered close these crowds make an ideal target. Moreover, you expect people to be moving in and out with large suitcases. This provides the perfect cover for an attack as it increases the difficulties in spotting someone suspicious. Currently, authorities are focused on enhancing security in these public areas.

Another dimension is that even a failed attack has costly consequences for governments. Umar Farouk Abdulmutallab, known as the underwear bomber, didn’t succeed. His plan to bring down an airliner probably cost $5,000 at the most. In response, the United States spent billions of dollars deploying full-body scanners. Likewise, the shoe bomber, Richard Reid, failed. His attempt had repercussions in adjusted security procedures for airports around the world. The result is the inconvenience of millions, as they removed their shoes for scanning. This slowed the security clearance process, adding to delays and passenger frustration. 

One attack, successful or otherwise, obliges governments to do something. This involves enhanced security at thousands of airports worldwide. Thus, it’s not the size of the attack that drives the diversion of resources to security. Rather the number of potentail targets that need protecting.

That’s why civil aviation and airports remain tempting targets. In cost/benefits terms, it gives the terrorist the most significant return for the least investment.