Instrument flight rules requirements fall into four buckets: a properly rated and current pilot, a legally equipped and inspected aircraft, a filed flight plan with an ATC clearance before entering controlled airspace, and compliance with the fuel, altitude, communication, and approach rules that govern the flight itself.1eCFR. 14 CFR 91.173 – ATC Clearance and Flight Plan Required Each piece is a separate legal hurdle, and missing any one of them makes the flight illegal even if the others are perfect.
Pilot Rating and Currency
Acting as pilot-in-command under IFR requires an instrument rating. To earn it, an applicant must log at least 40 hours of actual or simulated instrument time, with at least 15 of those hours received from a certified instructor holding the appropriate instrument rating, and then pass a practical test in an airplane, helicopter, powered-lift, or approved simulator.2eCFR. 14 CFR 61.65 – Instrument Rating Requirements
The rating alone is not enough. Within the preceding six calendar months, the pilot must have performed and logged six instrument approaches, holding procedures, and intercepting and tracking courses using navigation systems.3eCFR. 14 CFR 61.57 – Recent Flight Experience: Pilot in Command – Section: (c) Instrument Experience These tasks can be flown in actual instrument conditions or under simulated conditions with a view-limiting device and a safety pilot.
If that six-month window lapses, IFR privileges stop, but a second six-month grace period opens during which the pilot can regain currency by completing those same tasks with a safety pilot. After twelve months of lapsed currency, the only path back is an instrument proficiency check with a certified instructor or examiner covering all areas of operation from the instrument rating standards.4eCFR. 14 CFR 61.57 – Recent Flight Experience: Pilot in Command – Section: (d) Instrument Proficiency Check Flying IFR without the rating or without current experience can lead to certificate suspension or revocation.
Required Aircraft Equipment
Beyond the instruments required for daytime visual flight, an IFR aircraft must carry a generator or alternator, appropriate two-way radios and navigation equipment, an attitude indicator, a slip-skid indicator, a clock showing hours, minutes, and seconds, a sensitive altimeter adjustable for barometric pressure, a rate-of-turn indicator, and a directional gyro.5eCFR. 14 CFR 91.205 – Powered Civil Aircraft With Standard U.S. Airworthiness Certificates: Instrument and Equipment Requirements Aircraft equipped with a third attitude instrument covering full 360-degree pitch and roll are excepted from the rate-of-turn indicator requirement. Every item on the list must be installed and working before departure; one missing instrument makes the aircraft illegal for IFR.
Since January 2020, ADS-B Out equipment meeting specified technical standards has been required in Class A, B, and C airspace, within 30 nautical miles of major airports up to 10,000 feet, and in Class E airspace at and above 10,000 feet over the contiguous United States.6eCFR. 14 CFR 91.225 – Automatic Dependent Surveillance-Broadcast (ADS-B) Out Equipment and Use Because almost all IFR flight happens in that airspace, ADS-B Out is effectively mandatory for IFR operations.
Inspection Deadlines
Three recurring tests keep an aircraft legal for IFR. Miss any deadline and the aircraft is grounded from IFR until the test is completed.
- VOR equipment check within the preceding 30 days when VOR is used for IFR navigation, with the date, location, bearing error, and signature of the person performing the check entered in the aircraft records.7eCFR. 14 CFR 91.171 – VOR Equipment Check for IFR Operations
- Altimeter and static system tests every 24 calendar months, covering the static pressure system, each altimeter, and the automatic altitude reporting system.8eCFR. 14 CFR 91.411 – Altimeter System and Altitude Reporting Equipment Tests and Inspections
- ATC transponder tests on the same 24-calendar-month cycle.9eCFR. 14 CFR 91.413 – ATC Transponder Tests and Inspections
Flying with an expired inspection is an enforcement matter. The maximum civil penalty for an airman serving as an airman is $1,875 per violation as of 2025, and more serious violations, particularly those involving safety risk, can reach $17,062 per occurrence.10Federal Register. Revisions to Civil Penalty Amounts, 2025 Repeated or egregious violations can also trigger certificate action.
Preflight Planning
Before every IFR flight, the pilot-in-command must become familiar with all available information for the trip, including weather reports and forecasts, fuel requirements, alternatives if the flight cannot be completed as planned, any known traffic delays, and runway length data for airports of intended use.11eCFR. 14 CFR 91.103 – Preflight Action
Fuel
An IFR flight must carry enough fuel to reach the destination, then fly from the destination to the alternate airport if one is required, and then fly for an additional 45 minutes at normal cruising speed. Helicopters have a 30-minute reserve.12eCFR. 14 CFR 91.167 – Fuel Requirements for Flight in IFR Conditions That is the legal floor.
When an Alternate Is Required
An alternate airport does not have to be listed on the flight plan if the destination has a published instrument approach and the weather is forecast to have at least a 2,000-foot ceiling and 3 statute miles of visibility from one hour before to one hour after the estimated time of arrival.13eCFR. 14 CFR 91.169 – IFR Flight Plan: Information Required Fall below any of those thresholds and an alternate is required.
The alternate itself must also meet minimum weather standards at the estimated time of arrival: 600-foot ceiling and 2 statute miles of visibility for a precision approach, or 800 feet and 2 miles for a nonprecision approach. When the published approach procedure specifies different alternate minimums, those figures apply instead.13eCFR. 14 CFR 91.169 – IFR Flight Plan: Information Required
NOTAMs and TFRs
Notices to Air Missions cover temporary hazards, equipment outages, runway closures, and airspace restrictions that may not appear on charts. Temporary Flight Restrictions are communicated through NOTAMs, and the FAA investigates all reported TFR violations, with consequences ranging from warnings to certificate revocation.14Federal Aviation Administration. Temporary Flight Restrictions An IFR clearance does not by itself authorize you to enter a TFR; that requires explicit authorization.
Filing the Flight Plan and Getting a Clearance
The domestic IFR flight plan is filed on FAA Form 7233-1 through a flight service station or an electronic filing system such as Leidos Flight Service or ForeFlight.15Federal Aviation Administration. FAA Form 7233-1 – Flight Plan The form captures aircraft identification and type, equipment codes, true airspeed, departure point, route, cruising altitude, destination, estimated time en route, fuel on board, alternates, and the number of people on board. The FAA recommends filing at least 30 minutes before the estimated departure time to avoid clearance delays.16Federal Aviation Administration. ENR 1.10 – Flight Planning
Before entering controlled airspace under IFR, the pilot contacts clearance delivery and receives an ATC clearance that includes the clearance limit, route, initial altitude, departure frequency, and transponder code. The clearance must be read back accurately, and any misunderstanding is corrected before taxi.
At a towered airport, ATC closes the flight plan on landing. At a non-towered airport, or when the tower is closed, closing the flight plan is the pilot’s responsibility, done by radio to approach or center after landing, or by phone. Until it is closed, ATC treats the airport as occupied by IFR traffic, which can block other departures and arrivals.
Minimum IFR Altitudes
Except during takeoff and landing, an IFR flight must stay at or above the minimum altitudes published for the route. Where both a minimum en route altitude (MEA) and a minimum obstruction clearance altitude (MOCA) are published for a segment, the aircraft may descend to the MOCA only when navigation signals are receivable, and for VOR navigation only within 22 nautical miles of the VOR station.17eCFR. 14 CFR 91.177 – Minimum Altitudes for IFR Operations
Where no minimum altitude is published, the floor is 2,000 feet above the highest obstacle within 4 nautical miles of the course over designated mountainous areas, and 1,000 feet over non-mountainous terrain.17eCFR. 14 CFR 91.177 – Minimum Altitudes for IFR Operations
En Route Communications
The pilot-in-command must maintain a continuous watch on the assigned ATC frequency and report the time and altitude when passing designated reporting points (unless under radar control, where only specifically requested reports are needed), any unexpected weather, and anything else affecting flight safety as soon as possible.18eCFR. 14 CFR 91.183 – IFR Communications ATC altitude and heading instructions must be followed unless doing so would be unsafe.
Supplemental Oxygen
Oxygen rules apply regardless of weather. In unpressurized aircraft, the flight crew must use supplemental oxygen for any time above 12,500 feet cabin pressure altitude up to 14,000 feet that exceeds 30 minutes, and for the entire time above 14,000 feet. Above 15,000 feet, every occupant must be provided with supplemental oxygen.19eCFR. 14 CFR 91.211 – Supplemental Oxygen
Pressurized aircraft above flight level 250 must carry at least a 10-minute supply of supplemental oxygen for each occupant in case cabin pressurization fails. Above flight level 350, one pilot must wear and use an oxygen mask at all times, unless two pilots are at the controls and each has a quick-donning mask that can be secured within five seconds.19eCFR. 14 CFR 91.211 – Supplemental Oxygen
Instrument Approach Rules
Descending below the decision altitude on a precision approach, or the minimum descent altitude on a nonprecision approach, requires three conditions to be met at the same time. The aircraft must be in a position from which a normal descent to landing is possible; the flight visibility must be at least what the published approach procedure requires; and the pilot must be able to distinctly see at least one specific visual reference for the runway, such as the approach lights, the threshold or its markings, runway end identifier lights, the visual glideslope indicator, the touchdown zone, or the runway itself.20eCFR. 14 CFR 91.175 – Takeoff and Landing Under IFR
If the approach lights are the only visible reference, descent below 100 feet above the touchdown zone elevation is not permitted unless the red terminating bars or red side row bars are also distinctly visible.20eCFR. 14 CFR 91.175 – Takeoff and Landing Under IFR Reaching the missed approach point without the required visual references, or losing sight of the runway environment during a circling approach, requires a missed approach: climb to a safe altitude and fly the published missed approach procedure or the alternate instructions given by ATC.21Federal Aviation Administration. Arrival Procedures
Lost Communications
If the radio fails in visual conditions, or the aircraft breaks out of the clouds after the failure, the pilot continues under visual flight rules and lands as soon as practicable.22eCFR. 14 CFR 91.185 – IFR Operations: Two-Way Radio Communications Failure
If the failure occurs in instrument conditions with no way to get VFR, the route flown is whichever came most recently: the last route ATC assigned, the route ATC said to expect, or the route filed in the flight plan. Under radar vectors when the radio died, the pilot proceeds direct to the fix specified in the vector clearance and continues from there.22eCFR. 14 CFR 91.185 – IFR Operations: Two-Way Radio Communications Failure
The altitude flown is the highest of three: the altitude last assigned by ATC, the minimum IFR altitude for the segment, or the altitude ATC said to expect. At the clearance limit, the approach begins as close as possible to any expect-further-clearance time; if none was given, it begins at the originally estimated arrival time.22eCFR. 14 CFR 91.185 – IFR Operations: Two-Way Radio Communications Failure
Emergency Deviation Authority
In an in-flight emergency requiring immediate action, the pilot-in-command may deviate from any rule in Part 91 to the extent required to meet the emergency. A written report may be requested by the FAA afterward, explaining what happened and why the deviation was necessary.23eCFR. 14 CFR 91.3 – Responsibility and Authority of the Pilot in Command The authority is broad by design, because no rule can anticipate every scenario a pilot may face in instrument conditions.