IFR Weather Minimums: Takeoff, Approach, and Alternate Standards

What are IFR weather minimums and who sets them?

IFR weather minimums are the legally required ceiling and visibility values that govern when you may take off, continue an approach to landing, and file a flight plan without an alternate airport. They are established by Title 14 of the Code of Federal Regulations, with the primary authority for general aviation operations residing in 14 CFR Part 91 Subpart B.

Three regulatory sections control the majority of weather minimum questions on an instrument rating oral exam:

• 14 CFR 91.169 — IFR flight plan requirements, including the 1-2-3 rule for alternate exemption and the 600-2 / 800-2 alternate planning minimums.
• 14 CFR 91.175 — Takeoff and landing under IFR, including the 10 required visual references before descent below DA or MDA, and the commercial operator takeoff minimums under subsection (f).
• 14 CFR 91.157 — Special VFR weather minimums, covering the 1 sm / clear-of-clouds standard and the night restrictions.

The critical distinction every instrument student must internalize before the oral exam: Part 91 general aviation pilots and commercial operators under Parts 121, 125, 129, and 135 operate under significantly different takeoff minimum frameworks. The approach and alternate minimum rules, by contrast, apply broadly — published approach minimums come from the instrument approach procedure itself, which is established by FAA under 14 CFR 91.175(a).

What are the IFR takeoff minimums for Part 91 operations?

Part 91 pilots operating non-commercially have no federally published minimum ceiling or visibility for IFR takeoff. 14 CFR 91.175(f) explicitly restricts its takeoff minimum requirements to "persons operating an aircraft under part 121, 125, 129, or 135" — Part 91 is not listed.

This means a Part 91 PIC may legally depart IFR in zero-zero conditions, provided the aircraft is equipped for IFR flight per 14 CFR 91.205 and an IFR clearance has been obtained. Whether that decision is prudent is a separate question — DPEs will probe exactly this distinction on the oral exam.

What Part 91 pilots must know in practice:

• No federal ceiling or visibility minimum for takeoff — but your aircraft's departure procedure obstacle clearance requirements still apply.
• Many airports publish non-standard takeoff minimums in the Terminal Procedures Publication (TPP). These are regulatory for Part 121/135 but advisory for Part 91.
• Personal minimums and aircraft climb performance in IMC are the practical constraints — not a federal minimum.
• A DPE will ask what your personal minimums are and expect a thoughtful, reasoned answer grounded in training and experience.

The absence of a federal takeoff minimum for Part 91 is one of the most frequently tested contrasts in the instrument oral exam. Know it cold: the rule exists in 91.175(f), but it applies only to commercial operators.

What are the IFR takeoff minimums for Part 121 and Part 135 operations?

Commercial operators under Parts 121, 125, 129, and 135 must comply with published takeoff minimums. 14 CFR 91.175(f) prohibits a pilot from taking off from a civil airport under IFR unless "weather conditions at time of takeoff are at or above the weather minimums for that airport." When no takeoff minimums are published for an airport, the following defaults apply under 91.175(f)(2):

Beyond these defaults, individual certificate holders operating under Part 121 or Part 135 must comply with their operations specifications, which may impose higher takeoff minimums at specific airports or for specific operations. Under 14 CFR 121.651, airline pilots cannot begin takeoff unless weather conditions meet those specified in the certificate holder's operations specifications, or Parts 91 and 97 if ops specs do not specify. Under 14 CFR 135.225, commuter and on-demand operators face similar restrictions, and a straight-in-approach exception permits departure when weather equals the lowest straight-in landing minimums if wind and equipment conditions allow.

As an instrument-rated PIC under Part 91, you will not be tested on the specifics of ops-spec minimums — but you must understand that the regulatory framework for commercial operations is more restrictive, and that the published minimums in the TPP are mandatory for those operators.

How do approach minimums appear on an instrument approach plate?

Approach minimums are published in the minimums section of each instrument approach procedure, approved under 14 CFR 91.175(a) by reference to Part 97. The plate presents minimums by aircraft category (A, B, C, D) and approach type, and expresses them either as a decision altitude/height (DA/DH) for precision approaches or a minimum descent altitude (MDA) for non-precision approaches.

Understanding the difference between DA and MDA is fundamental:

• Decision Altitude (DA) — Used on precision approaches (ILS, LPV). The altitude at which you must initiate a missed approach if you have not established the required visual references. You do not level off at DA — it is a decision point reached during a continuous descent.
• Minimum Descent Altitude (MDA) — Used on non-precision approaches (VOR, NDB, LNAV). The lowest altitude to which you may descend during the final approach segment without the required visual references. You level off at the MDA and fly horizontally until either the runway environment appears or you reach the missed approach point.

The approach plate also publishes the required visibility in either statute miles or runway visual range (RVR). RVR is expressed in hundreds of feet (e.g., RVR 2400 = 2,400 feet of runway visual range). The FAA Instrument Procedures Handbook (FAA-H-8083-16B) provides detailed guidance on reading approach charts and interpreting minimums for your aircraft category.

What visual references does 91.175(c) require before descending below DA or MDA?

14 CFR 91.175(c) prohibits descent below the DA or MDA, and prohibits continuing past the missed approach point, unless the aircraft is in a position to make a normal landing and the pilot can distinctly identify at least one of the following runway environment elements. This is the complete list:

1. 1
   Approach light system — but see the 100-foot restriction below
2. 2
   Runway threshold
3. 3
   Threshold markings
4. 4
   Threshold lights
5. 5
   Runway end identifier lights (REIL)
6. 6
   Visual glideslope indicator (VASI or PAPI)
7. 7
   Touchdown zone or touchdown zone markings
8. 8
   Touchdown zone lights
9. 9
   Runway or runway markings
10. 10
    Runway lights

The approach lights restriction: If the only visual reference you have is the approach light system — and you cannot see any of the runway environment elements listed above it — you may descend below the DA or MDA but you may not descend below 100 feet above the touchdown zone elevation (TDZE). This is explicit in 91.175(c)(1): a pilot who sees only approach lights "may descend to 100 feet above the touchdown zone elevation."

This 100-foot limitation is a high-frequency oral exam topic. The correct answer: approach lights alone take you to 100 feet above TDZE, no lower. Any one of the other nine references, combined with the aircraft being in a position to make a normal landing, takes you to the published DA or MDA.

What are the alternate airport minimums under 91.169, and what is the 1-2-3 rule?

14 CFR 91.169(b) provides the conditions under which you do not need to list an alternate airport on your IFR flight plan. For non-helicopter operations, no alternate is required if the destination airport has a published standard or special instrument approach procedure AND weather is forecast to be at least a 2,000-foot ceiling and 3 statute miles visibility from 1 hour before to 1 hour after your estimated time of arrival. This is universally known as the 1-2-3 rule.

The key word is forecast — you apply the 1-2-3 rule to the TAF at your destination, not to current observations. If the TAF shows a temporary or becoming condition that drops below 2,000/3 within your ETA window, you must file an alternate.

When an alternate is required, 14 CFR 91.169(c) governs what weather must be forecast at that alternate airport at your estimated time of arrival:

These are planning minimums — values you apply when selecting your alternate during preflight planning. They are not the minimums you must actually encounter at the alternate when you arrive; if weather deteriorates after departure, you use the published approach minimums for the actual approach, not the 600/800 planning floor.

What do non-standard alternate minimums look like on a plate?

Not all airports may be used as IFR alternates under standard minimums, and some airports cannot be used as alternates at all. Two symbols in the briefing strip of an instrument approach plate signal this:

• Circled "A" symbol — Non-standard alternate minimums apply. You cannot use the standard 600-2 / 800-2 values. You must look up the specific minimums for that airport in the Alternate Minimums section of the Terminal Procedures Publication (TPP). The alternate minimums there may require higher ceilings, greater visibility, or operational equipment (e.g., DME or a working approach lighting system).
• "NA" (Not Authorized) — This airport may not be used as an IFR alternate under any conditions. Common reasons: no weather reporting facility, no approved instrument approach procedure, or a required navigational aid routinely out of service.

The distinction between the circled A and NA is another common oral exam question. If you see NA at an airport you were planning to use as your alternate, you must choose a different alternate — there is no workaround. If you see the circled A, you must look up and apply the actual published minimums rather than assuming the standard values.

What is Special VFR and how does it relate to IFR minimums?

Special VFR is a clearance that allows flight within a Class B, C, D, or E surface area in weather conditions below the basic VFR minimums of 14 CFR 91.155. It is not an IFR clearance and does not require an IFR-equipped aircraft or instrument rating — during daytime operations.

Under 14 CFR 91.157:

• Special VFR requires an ATC clearance.
• The pilot must maintain at least 1 statute mile flight visibility and remain clear of clouds.
• For night Special VFR: the pilot must hold an instrument rating meeting Part 61 requirements, and the aircraft must be equipped for IFR flight per 14 CFR 91.205(d).
• Some high-traffic airports prohibit Special VFR entirely — these are listed in Appendix D, Section 3 of Part 91.
• Helicopters are exempt from the visibility requirement and time-of-day restrictions.

Special VFR is an adjacent topic to IFR minimums because it represents a middle ground: it allows departure or arrival in conditions that do not meet VFR but do not require a full IFR clearance. A DPE will distinguish whether you understand when to request a Special VFR clearance versus filing IFR. If you are instrument-rated and in IMC, the appropriate tool is an IFR clearance — Special VFR is better suited to situations where you are just below VFR conditions and want to get out of a surface area to reach VMC.

How do DPEs examine IFR weather minimums on the oral?

DPEs typically approach IFR weather minimums through a scenario, not a recitation quiz. They present a departure airport, destination, and a weather package, then ask you to work through the decisions. Common oral exam threads and the regulation each one traces to:

• "Is an alternate required for this flight?" — Traces to 91.169(b). Evaluate the TAF at the destination against the 1-2-3 rule: 2,000-foot ceiling and 3 sm visibility from 1 hour before to 1 hour after your ETA.
• "You chose KXYZ as your alternate. What minimums must the forecast there show?" — Traces to 91.169(c). Identify the best approach at the alternate (precision vs. non-precision) and apply 600-2 or 800-2 accordingly.
• "The ATIS at your destination shows 200-foot overcast and RVR 1200. Can you shoot the ILS?" — Traces to 91.175(c). You can initiate the approach as long as conditions met minimums when you started (Part 91 has latitude here). At DA, you need one of the 10 references in sight.
• "You're at MDA on the VOR approach and you can only see the approach lights. What do you do?" — Traces to 91.175(c)(1). You may continue to 100 feet above TDZE. Below that altitude without additional runway environment references, you must execute the missed approach.
• "You're departing in a quarter-mile fog. Is that legal under Part 91?" — Traces to 91.175(f). No federal minimum exists for Part 91 takeoff; it is legal but may be inadvisable. Expect a follow-up on personal minimums and obstacle clearance.

The underlying theme in every scenario: the DPE is verifying that you know which regulation applies, what it says, and how you apply it to the specific facts in front of you. Stating "I need an alternate" without citing 91.169 is an incomplete answer. Stating "I need an alternate because 91.169(b) requires one when the TAF shows below 2,000 and 3 miles within my ETA window" is the answer that gets you through.

Frequently Asked Questions

Q: What is the 1-2-3 rule for IFR alternate airports?

Under 14 CFR 91.169(b), you do not need to file an alternate if a standard or special instrument approach procedure exists at your destination and weather is forecast to be at least 2,000 feet ceiling and 3 statute miles visibility from 1 hour before through 1 hour after your estimated time of arrival. This is universally called the 1-2-3 rule.

Q: What are the alternate airport minimums for a precision approach?

Under 14 CFR 91.169(c), if you list an airport as your alternate and it has a precision approach procedure, the planning minimums are a 600-foot ceiling and 2 statute miles visibility. For a non-precision approach, the minimums increase to an 800-foot ceiling and 2 statute miles visibility.

Q: Do Part 91 pilots have published takeoff minimums?

No. 14 CFR 91.175(f) restricts IFR takeoff minimums only to operators under Parts 121, 125, 129, and 135. A Part 91 PIC has no federally published minimum ceiling or visibility for takeoff, though personal minimums and aircraft performance remain the pilot's responsibility.

Q: How many visual references must you see before descending below DA or MDA?

Under 14 CFR 91.175(c), you must have at least one of 10 specific runway environment references distinctly in sight, and the aircraft must be in a position to make a normal landing, before descending below DA or MDA. Seeing only approach lights permits descent to 100 feet above TDZE — no lower without additional references.

Q: What does a circled 'A' or 'NA' mean on an instrument approach plate?

NA (Not Authorized) in the alternate minimums box means the airport may not be used as an IFR alternate under any conditions. A circled 'A' symbol means non-standard alternate minimums apply — you must consult the Alternate Minimums section of the Terminal Procedures Publication for the actual required ceiling and visibility.

Q: Can you fly a Special VFR clearance at night?

Yes, but only if you hold an instrument rating meeting 14 CFR 61 requirements and your aircraft is equipped for IFR flight per 14 CFR 91.205(d). Without both conditions, Special VFR is restricted to daytime operations under 14 CFR 91.157.

Q: What are the default IFR takeoff minimums for commercial operators when none are published?

Under 14 CFR 91.175(f)(2), the default IFR takeoff minimums for Part 121/125/129/135 operators are 1 statute mile visibility for single and twin-engine aircraft, and 1/2 statute mile visibility for aircraft with 3 or more engines and for helicopters.

Q: What is the difference between DA and MDA on an instrument approach?

A decision altitude (DA) is used on precision approaches (ILS, LPV). You execute a missed approach if visual references are not established at DA. A minimum descent altitude (MDA) applies to non-precision approaches — you may not descend below it unless the runway environment is in sight and you can make a normal landing.

Sources

• 14 CFR 91.169 — IFR Flight Plan: Information Required (Cornell LII)
• 14 CFR 91.175 — Takeoff and Landing Under IFR (Cornell LII)
• 14 CFR 91.157 — Special VFR Weather Minimums (Cornell LII)
• 14 CFR 121.651 — Takeoff and Landing Weather Minimums: Supplemental Operations (Cornell LII)
• 14 CFR 135.225 — IFR: Takeoff, Approach, and Landing Minimums (Cornell LII)
• FAA Instrument Flying Handbook (FAA-H-8083-15B)
• FAA Instrument Procedures Handbook (FAA-H-8083-16B)
• FAA Aeronautical Information Manual (AIM)

This article was researched from FAA primary sources (14 CFR Parts 91, 121, and 135 via Cornell LII; Instrument Flying Handbook FAA-H-8083-15B; Instrument Procedures Handbook FAA-H-8083-16B; Aeronautical Information Manual) and citing current regulatory text — drafted by MockDPE. Last updated: May 2026. If you spot an inaccuracy, email corrections@mockdpe.org.