I would not just ignore it. This will cause your horse to become a "sissy" You need to build up his confidence of not being afraid of anything. One rein stop him and then approach and retreat is what I do. Ignoring the problem is not going to do anything.
I have to respectfully disagree. Ignoring it doesn't cause your horse to be a sissy. It can cause your horse to be more focused on you (the rider) and less focused on whatever is scaring him.
Also, you can't tell your horse not to ever be afraid. Fear is a natural thing for all animals, horses and humans. He's going to be afraid, but the intensity of the fear is what you can change and lessen (from a big jump sideways spook or a bolting spook to a spook in place)....by way of keeping him busy/redirecting that moment of nervous energy.
Ignoring it can simply mean that you don't react to the spook/spooky object (as long as it's not a runaway truck barreling at you at 50 mph
If you always take the time to approach the spooky thing (approach and retreat) this can backfire and cause a "sissy" horse....because what you might be doing is telling the horse "look at everything that might scare you" vs. pay attention to me despite the spooky thing and your horse might get the habit of looking for things to spook at.
-One rein stop and go on with your life
-Disengage the hindquarters quickly - sending the energy through the hip, so to speak...when the horse relaxes, release and walk on...
-Ask for change of direction, stop, back up, shoulder move over, give to the bit, speed up, slow down, etc.... take charge of the situation and the horse can calm down faster because he can't think of too many things at once. So, either he thinks of you or the spooky thing.
The basic idea is that you train yourself not to react to the spooking horse. If you clamp your legs around him or pull back on both reins when he spooks, you can become part of the problem. Instead, redirect and stay in control.