My 19 month daughter spotted a drone in the park today, and she was quite interested. We maneuvered her tricycle towards it and got up close. The man flying the thing brought it over to show it to her, hovering close to the ground. He and I talked a bit, and then he took it up a bit into the air, but still not too far away. The more power he gave it, the louder it got.
A couple moments later, my daughter turned around in her tricycle seat, visibly upset. "Daddy hold you! Daddy hold you!" By the times I got her into my arms, her face was quivering with fear.
There are two well-intended ways I could have handled this situation.
(1) "You don't have to worry about this drone. It isn't going to hurt you. Look, the man has it and it won't come any closer. I know it's loud but the loudness can't hurt you. It's just loud."
(2) "I gotcha. Let me pick you up. I want you right here safe in my arms. I am so sorry that you got scared. That loud noise is scary isn't it? Well, you know what, I'm going to keep holding you and we're going to walk away from it. You can keep watching it but we are going to get away. I gotcha. That drone was scary wasn't it? It was exciting too but very loud and scary. But, don't worry, I gotcha. I'm not going to put you down. Let's keep walking and look at it from far away."
The first reply was a very well intended one that has been issued by many parents, especially fathers. We want to try to help dissipate the fear by rationally explaining to our son or daughter about why they don't need to be afraid of something. However, the reality is that our child at the age of 19 months hasn't even grown most of their cognitive brain by this point, so it's almost like it's going in one ear and out the other.
The second reply is meeting our child right where they're at. By first creating a sense of safety with them, we help them to calm down right away. In this case, I took my daughter into my arms and right out of the situation. That already began to help calm her. The second thing I did was to help her identify her feeling with a word. I know it might seem hard to believe, but a 19 month old can probably identify "scary" even if they can't produce the word. In any case, they know you are giving them a word to name their feeling, and moreover, they feel like you are connecting with them intimately.
Thus, the child of the second parent knows they have been made safe, feel emotionally connected, and have been given a word to name the feeling they are experiencing. John Gottman's research, among others, shows that this is one of the best ways to help a child learn how to regulate their own emotions in the future, in addition to the moment ("How to Raise an Emotionally Intelligent Child" p. 93).
It might sound counter-intutitive, but the child who receives safety, comfort, and emotional connection will ultimately grow up to a higher level of emotional stability and self-soothing. They will fear less in general, or at minimum, they will learn how to sooth themselves via self or others when they do feel fear. Also, in a counter-intuitive way, the child of the parent who tries to explain away their fears will wallow in their fears much longer and more frequently over time, unable to learn how to calm down in future situations. The parent in scenario is well meaning, but will not be successful in helping their child grow emotionally or learn how to problem solve very well.
(photo taken from flickr creative commons with permission from Richard Unten at https://www.flickr.com/photos/unten44/)