Operating an aircraft under the influence is a crime in Montana and a violation of federal aviation regulations. The state offense is a misdemeanor in the aeronautics code, MCA § 67-1-204(7), and it is stricter than the driving law in two ways: the definition of impairment and the alcohol number. This page explains the state statute and how the federal rules sit beside it. It is part of our Montana DUI Guide.
Montana's Statute
The prohibition reads: "A person may not knowingly operate, attempt to operate, or be in actual physical control of an aircraft while under the influence of alcohol or drugs." The same subsection defines the key phrase for this offense: "as a result of taking into the body alcohol, drugs, or any combination of alcohol and drugs, a person's ability to safely operate the aircraft has been diminished to the slightest degree" (MCA § 67-1-204(7)).
Three features are worth noticing:
- Attempt counts. The statute reaches a person who attempts to operate, and a person in actual physical control, not only a pilot in flight.
- "Aircraft" is defined broadly as "a contrivance used or designed for navigation of or flight in the air" (MCA § 67-1-101).
- There is a reporting duty. A person having information regarding a violation "shall report the information to the department" (MCA § 67-1-204(8)). That subsection is the one part of the statute excluded from the criminal penalty.
How It Differs From a DUI in a Car
| Point | DUI on the road | Aircraft |
|---|---|---|
| Statute | MCA § 61-8-1002 | MCA § 67-1-204(7) |
| Conduct | Drives or is in actual physical control of a vehicle | Operates, attempts to operate, or is in actual physical control of an aircraft |
| Mental state | Absolute liability (§ 61-8-1002(5)) | The statute says "knowingly" |
| Under the influence | Ability to safely operate has been diminished | Ability to safely operate the aircraft has been diminished to the slightest degree |
| Alcohol number | 0.08 per se offense for most drivers | At 0.04 or more it may be inferred a crewmember is under the influence (§ 67-1-211(1)) |
| Penalty | Set by § 61-8-1007 | Fine up to $500, up to 6 months in jail, or both (§ 67-1-205) |
| Test refusal | Driver's license suspension | No test is given; refusal is admissible (§ 67-1-211(5)) |
The aircraft offense is not part of the DUI statutes, and the aeronautics penalty section does not provide for a driver's license suspension. For a pilot, the consequence that matters most is usually the federal one.
The 0.04 Inference and Other Evidence
If a person acting or attempting to act as a crewmember has an alcohol concentration of 0.04 or more, "it may be inferred that the person is under the influence of alcohol" and in violation of the statute (MCA § 67-1-211(1)). That is an inference, not an automatic conviction, and the statute still requires proof of the offense.
Evidence of any measured amount of alcohol is admissible, along with other competent evidence of whether the person was under the influence of alcohol, drugs, or both. The statute also lets the court or jury "consider federal regulations governing aeronautics" (MCA § 67-1-211(2), (3)). The testing procedures used in DUI cases apply (MCA § 67-1-211(6)), so the questions we raise about how alcohol concentration is measured apply here as well.
Testing and Refusal Under State Law
A person who operates an aircraft over the lands and waters of Montana is considered to have consented to a test of blood, breath, oral fluid, or urine if arrested by a peace officer for operating, attempting to operate, or being in actual physical control of an aircraft while under the influence. The officer must have reasonable grounds and may choose the test (MCA § 67-1-211(4)).
If the person refuses, "a test will not be given, but proof of refusal is admissible" (MCA § 67-1-211(5)). The aeronautics statute does not attach a driver's license suspension to that refusal, unlike a refusal after a DUI arrest on the road. The federal consequences of a refusal are a separate matter, covered next.
The Federal Rules: 14 CFR § 91.17
The Federal Aviation Regulations say that no person may act or attempt to act as a crewmember of a civil aircraft:
- within 8 hours after the consumption of any alcoholic beverage;
- while under the influence of alcohol;
- while using any drug that affects the person's faculties in any way contrary to safety; or
- while having an alcohol concentration of 0.04 or greater in a blood or breath specimen.
A crewmember must submit to an alcohol test at the request of a law enforcement officer who is authorized under state or local law to conduct it and is investigating a suspected violation of a state or local law covering the same conduct (14 CFR § 91.17(c)). Montana's statute is that kind of law.
What the FAA Can Do to a Certificate
Committing an act prohibited by § 91.17(a) is grounds for denying an application for a certificate or rating for up to 1 year after the act, or for suspending or revoking any certificate, rating, or authorization (14 CFR § 61.15(b)). Refusing a test requested under § 91.17(c), or refusing to furnish test results the FAA requests, carries the same grounds (14 CFR § 61.16).
These are administrative actions by a federal agency. They do not depend on a conviction in state court, and an acquittal or dismissal in the criminal case does not by itself end them. A&M Law is a Missoula firm that defends DUI cases in Western Montana, and FAA certificate work is a different field. A pilot facing FAA certificate action should talk to a lawyer who practices aviation law, and should do so before making statements to the agency.
If You Are a Pilot Charged With an Ordinary DUI
Most pilots who call a DUI lawyer were arrested in a car, not a cockpit. The FAA's rules reach that situation too, through the "motor vehicle action" reporting requirement in 14 CFR § 61.15. The deadline is short and runs from the conviction or the license action, so it should be on the table from the first meeting. See pilots and FAA reporting and our general page on jobs, licenses, and gun rights after a DUI.
This page explains Montana and federal law in general as of October 2026. It is not legal advice about your specific case, and it is not advice about FAA medical or certificate matters.