Alcohol
It is obvious that flying airplanes and alcohol do not mix. However, it is common for pilots to underestimate the lasting effects of alcohol consumption. A pilot might feel fine to fly, but be suffering from the influence or after effects of alcohol more than a 24 hours later.
The legal requirements for pilots concerning alcohol consumption is "Eight hours bottle to throttle", with the additional stipulation which specifies a blood alcohol content no greater than 0.04%.
Most aviation businesses do not allow their pilots to follow these minimum legal requirements. Instead, its common for company policy to require 12 or even 24 hours bottle to throttle, with a zero tolerance for blood alcohol content.
The private pilot has the option of what personal policies to follow. For many people, it is advisable to follow the example of aviation business and adhere to a higher standard than the legal minimums.
It is also illegal to carry a person under the influence of drugs or alcohol, with the exception of an emergency or the carriage of a medical patient under proper care.
Drugs
Determining whether a medication is suitable for a pilot can be difficult. Often, a doctor or pharmacist can provide guidance for each specific drug. In general, it is important to avoid drugs which may effect the nervous system, since these drugs would effect flying ability directly.
The following medications are examples of those which have such effects and must be avoided:
If you need a prescription for a drug you are not sure is compatible with flying, discuss what options are available for you with your doctor or aviation medical examiner.
Carriage of Illegal Drugs
It is illegal to knowingly carry narcotics, marihuana, or depressant or stimulant drugs or other substances on an airplane.
Pilots Involved with Alcohol or Drugs
If a pilot is convicted of anything related to illegal drugs, the FAA may suspend or revoke that person's pilot's certificate. The FAA may also impose a 1 year waiting period before that person may reapply to take the written and practical tests to acquire pilot certification.
This is also true of a pilot who flies while under the influence or knowingly carries illegal drugs.
If a pilot is involved in a motor vehicle action, that pilot must report the motor vehicle action in writing to the FAA within 60 days. A motor vehicle action is basically anything that results from drinking and driving. Failure to report DUI related actions to the FAA can result in revocation of a person's pilot certificate and denial for application for one year.