A pilot may not touch a drink within 8 hours of flying, and may not fly at all with an alcohol concentration of 0.04 or higher. That is half the limit most US states set for driving a car. Both numbers are written into federal regulation, and neither depends on whether the pilot feels fine.
Everything below comes from the regulations themselves, 14 CFR 91.17 for the rules on flying, and 14 CFR Part 120 for testing.
The four separate prohibitions
People remember this as one rule about eight hours. It is actually four, and breaking any one of them is enough.
No person may act, or attempt to act, as a crewmember of a civil aircraft:
| Prohibition | What it means in practice |
|---|---|
| Within 8 hours after consuming any alcoholic beverage | A clock, not a judgement. One drink starts it. |
| While under the influence of alcohol | Can apply well past 8 hours |
| While using any drug that affects the person’s faculties contrary to safety | Includes prescriptions and over the counter medicines |
| With an alcohol concentration of 0.04 or greater | Half the usual driving limit |
The third one surprises people most. It is not a list of banned substances. It is a test of effect, so an ordinary cold remedy bought in a supermarket can put a pilot in breach of it.
Note also the words “or attempt to act”. A pilot who is stopped in the jet bridge has still attempted, and the regulation already covers them.
Why 0.04 and not 0.08
The driving limit across most of the United States is 0.08. Aviation sets half that.
The regulation defines the measure precisely, as grams of alcohol per deciliter of blood or per 210 litres of breath. It does not offer a sliding scale, a tolerance allowance or any recognition that individuals differ. At 0.04 you are done, whatever your size and whatever you feel.
There is a second reason the aviation number is stricter that is easy to miss. A cabin at altitude already puts a crew at the equivalent of several thousand feet of elevation. Alcohol and mild hypoxia do not cancel out.
When pilots actually get tested
Testing is not occasional. Part 120 sets out five separate circumstances, and the random programme is far larger than most passengers assume.
- Pre employment. Before performing a safety sensitive function at all. The rule explicitly stretches the definition of covered employee to include applicants, so there is no gap to slip through.
- Random. Continuous and unannounced, covered below.
- Post accident. Failing to remain available for post accident testing is itself treated as a refusal.
- Reasonable suspicion. On a documented determination by the employer.
- Return to duty. Required before anyone comes back after a verified positive or a refusal.
A refusal is not a neutral act. The regulation defines refusing to submit as its own violation, with the same consequences as a positive result.
The random testing rate, which is the striking part
The baseline minimum for random drug testing is 50 percent of all covered employees per year. The FAA may lower it to 25 percent only if the reported positive rate stays below 1.0 percent for two consecutive calendar years.
Random alcohol testing works the same way at lower numbers. A 25 percent rate may be lowered to 10 percent if the violation rate stays below 0.5 percent across two consecutive years.
Read that mechanism rather than just the figures. The rate is not fixed by opinion, it is tied to measured results, and it ratchets back up if the numbers worsen. The industry earns its lower testing rate by staying clean, and can lose it.
What happens if a police officer asks
A crewmember must submit to a blood or breath test on the request of a law enforcement officer, where that officer is authorised under state or local law to conduct it or have it conducted. The FAA can also require the results to be released to it.
So the common belief that this is purely an internal airline matter is wrong. Local police can act, and the federal regulator can obtain what they find.
What this means for a passenger
Stories about a pilot removed from a flight before departure tend to be read as evidence that something is badly wrong. The opposite is closer to the truth. Those pilots are almost always caught before the aircraft moves, by exactly the layered system described above: a colleague, a gate agent, a random test or a reasonable suspicion referral.
A system that never produced such a story would not be a system with no problem. It would be a system that was not looking.
Frequently asked questions
How long before a flight can a pilot drink?
No alcohol within 8 hours of acting or attempting to act as a crewmember. The 8 hours is a hard floor, not a guideline, and the separate prohibitions on being under the influence and on being at 0.04 or above still apply after it has passed.
What is the alcohol limit for pilots?
An alcohol concentration of 0.04 or greater is prohibited, measured as grams per deciliter of blood or per 210 litres of breath. That is half the usual 0.08 driving limit in the United States.
How often are pilots drug tested?
The minimum random drug testing rate is 50 percent of covered employees a year, reducible to 25 percent only when the reported positive rate stays under 1.0 percent for two consecutive years. Testing also happens pre employment, post accident, on reasonable suspicion and before return to duty.
Can a pilot take prescription medication?
The rule bans using any drug that affects the person’s faculties in a way contrary to safety. It is written around effect rather than a banned list, so prescription and over the counter medicines can both fall inside it.
Can police breathalyse a pilot?
Yes. A crewmember must submit to a blood or breath test when requested by a law enforcement officer who is authorised under state or local law to conduct it, and the FAA may require the results.
Sources
The prohibitions, the 0.04 figure, the definition of alcohol concentration and the law enforcement testing requirement are quoted from 14 CFR 91.17. The testing circumstances, the random rates and the conditions for lowering them are from 14 CFR Part 120. Both were read from the current edition on 5 October 2026. These are US rules; other regulators set their own limits, and several are stricter still.
More from CrewDaily: how long a pilot can legally fly in one day, what happens if both pilots fall asleep, and when pilots have to retire.
