There is nothing wrong with taking prescription drugs for fear of flying. Many people find these drugs safe and effective, and a life-saver! Assuming you don’t fly three times a week, then the drugs of choice for you will probably be a benzodiazepine. The common prescriptions are Valium, Lorazepam and Xanax.
These drugs are addictive but that is a problem for regular users, not occasional users. If you fly once a month and take one or even a couple of tablets you are unlikely to suffer any withdrawals (but be careful-even using them regularly for just a few weeks can cause a lot of problems).
How effective they are depends on how much you take and how your body handles them. Many people find that they make flying easy, and in some cases have even cured the fear of flying by leading the brain to make a positive association with flying rather than a negative one! There is a personal experience of Valium here.
For others, the drugs just take the edge of the fear and allow them to keep in control. You will have to experiment.
Don’t be tempted by online pharmacies: their over-priced products may not be subject to rigorous safety testing and you can’t trust them with your credit cards. A sympathetic doctor will normally be happy to prescribe for occasional uses such as flying.