Airdropping is a technique frequently used by startup businesses that are conducting an ICO to increase brand exposure and drum up excitement about their project. Airdrops are analogous to free samples at the mall (if those samples could appreciate in value). I'm here completely on santawarriors side. Not all airdrops are legit, as ICOs and their currency can be scams. However, don't mix it up with an ICO, which doesn't work out as expected

That's then just a flop but not a scam.
Nevertheless, there are several ways to check if the ICO or the currency is a scam or not. The easiest and most obvious way would be to check the white paper. Further, take a closer look at the homepage of the company. And an even more closer look at their team.