Hi.
It sounds as though you have a phobia--a strong fear that is persistent and doesn't diminish on its own. The good news is that there are ways to treat your phobia before you need to travel this coming summer.
You might start by asking your parents if they will allow you to see a doctor about this. A doctor can be a psychologist, psychiatrist, therapist or your primary care physician, if a referral is needed. A mental health provider can help you learn better ways to deal with your fear, like using meditation or relaxation exercises to feel more in control of the situation.
Therapists often find it helpful to confront the situation head-on with their client by having them practice being in the situation that scares them. For example, if you were afraid of heights, you and your therapist might work up to climbing a steep set of stairs together. But since planes are not as accessible as staircases, your therapist might choose to help you to visualize the situation, taking you step-by-step through the process of flying virtually.
There are certain medications that have been found helpful in treating phobias, too, but this is something you'll have to discuss with your doctor after a thorough evaluation.
It may take a while for your phobia to be controlled--sometimes treatment takes weeks or months--so I'd suggest you begin to look into these options as soon as possible.
Good luck and have a great time abroad!