Patients often come to us requesting the doctor or nurse to prescribe diazepam for fear of flying or assist with sleep during flights. Diazepam is a sedative, which means it makes you sleepy and more relaxed. There are a number of very good reasons why prescribing this drug is not recommended.
According to the prescribing guidelines doctors follow (British National Formulary) diazepam is contraindicated (not allowed) in treating phobic states. It also states that the use of benzodiazepines to treat short-term mild anxiety is inappropriate
Your doctor would be taking a significant legal risk by prescribing against these guidelines. They are only licensed short term for a crisis in generalised anxiety. If this is the case, you should be getting proper care and support for your mental health and not going on a flight.