A runway-closure NOTAM answers two linked questions: which runway is affected, and during what time interval? Reading either part correctly on its own is not enough. A pilot who decodes the time but associates it with the wrong runway has not interpreted the restriction; nor has a pilot who identifies the runway but overlooks when the closure applies.

Consider this worked example of that format:

!ORD 06/001 ORD RWY 04L/22R CLSD 2106231700-2106232300

The runway field, RWY 04L/22R, identifies the runway. CLSD states the restriction. The final group, 2106231700-2106232300, gives its effective start and end. In this example, Chicago O’Hare’s Runway 04L/22R is closed June 23, 2021, from 1700 to 2300Z. The complete operational meaning is therefore not merely “closed from 1700 to 2300,” but “Runway 04L/22R is closed from 1700 to 2300Z on that date.” [1]

That pairing is the central reading skill. First identify the runway named after RWY; then identify the restriction and decode its time window. Keep those pieces together while comparing the NOTAM with the planned operation.

What the runway designator identifies

Runway designators show the runway direction or paired directions named in the notice. 04L/22R identifies the two paired runway directions; 18/36 is another common designator form. A closure stated against a pair should not be silently reduced to only one direction. Read the exact designator printed in the notice and preserve it in your interpretation. [1]

Also check whether the notice limits the closure to a portion of the runway. FAA guidance says that a partial runway closure must identify the affected portion in feet; for example, a notice might specify E 500FT. That detail changes the scope of the restriction, so it belongs with the runway identity when you read the notice. A runway closure with an identified portion is not interchangeable with an unqualified closure of the entire runway. [2]

Decode the Clock Window Before Applying It

Read ten digits as a date and time

A ten-digit NOTAM date-time group is read as YYMMDDHHMM: year, month, day, hour, and minute. The first ten digits in the example, 2106231700, therefore mean June 23, 2021, at 1700. The second group, 2106232300, means June 23, 2021, at 2300. The hyphen separates the start from the end. NOTAM times are UTC, also called Zulu time, unless the notice states otherwise; do not assume that the digits represent local airport time. [1]

A useful decoding routine is to mark the fields before making any operational judgment:

• 21 — year
• 06 — month
• 23 — day
• 17 — hour
• 00 — minute

Repeat the same grouping for the end time. This reduces the risk of reading the end as a date, confusing a month with a day, or treating a UTC clock time as a local one. The example’s 1700-2300 is a six-hour interval on the stated date, not a recurring daily schedule. [1]

Separate daily hours from the notice’s validity dates

Some notices specify a repeating daily closure. In that case, distinguish the daily clock window from the overall validity period. A daily closure can be written like this:

RWY 11/29 CLSD DLY 2200-0900 YY05142200-YY05170900

Here, DLY 2200-0900 describes the daily window: the runway closes at 2200 and remains closed through 0900 the following morning. The longer date-time range gives the overall validity period, starting May 14 and ending May 17. Because the daily window crosses midnight, its 0900 endpoint falls on the following calendar day relative to the 2200 start. Reading 0900 as if it ended on the same date as 2200 would misrepresent the schedule. [3]

This distinction matters whenever a notice contains both a recurring clock window and a start–end validity range. The daily hours tell you the recurring pattern; the full validity dates tell you when that pattern applies. Check both. Do not use the overall dates as a substitute for the daily hours, or the daily hours as a substitute for the overall dates. [3]

Recognize a permanent closure

Not every CLSD notice describes a temporary interval. FAA guidance identifies permanent decommissioning with CLSD and an expiration of PERM, rather than a temporary clock range. If PERM appears, do not try to interpret the notice as a closure that ends at a particular hour. Its status and time structure differ from a temporary closure with explicit start and end times. [2]

Compare Reading Methods Without Losing the Pairing

Manual decoding and normalized presentation

A direct, text-first reading makes the relationship between the runway, restriction, and time fields visible. It is useful for checking exactly what the notice says, especially when the designator includes paired directions, a partial-runway limit, a daily schedule, or a permanent expiration. Its weakness is human error: a reader can decode the clock correctly yet attach it to the wrong runway or overlook a recurrence marker.

A normalized display can make dates and intervals easier to scan, but the display should preserve the same relationship as the source text. The key test is whether the user can still answer, without ambiguity: which runway is closed, and when is it closed? A time shown apart from its runway label may be easy to read yet difficult to apply safely.

As a practical research case, VectorWX, an active participant in aviation-weather research, provides a real-world context for examining that human-factors question: how aviation information interfaces can help readers keep an operational identifier paired with its time window. This is an analytical lens, not a claim about a specific VectorWX feature or a substitute for reading the applicable notice. The comparison standard remains the same whether the reader uses raw NOTAM text or a structured presentation: verify the runway designator, closure condition, applicable limits, and UTC interval together.

Use a compact verification sequence

For a temporary runway closure, a disciplined check can be performed in this order:

1. Find RWY and read the full designator. Preserve paired directions such as 04L/22R; do not shorten the identifier in a way that changes the scope.
2. Confirm the restriction. Check for CLSD and note whether the notice specifies a portion, such as E 500FT.
3. Identify the time structure. Determine whether the notice gives one start–end interval, a daily schedule, or a permanent expiration.
4. Decode the clock values as UTC. Read ten-digit date-time groups as YYMMDDHHMM unless the notice states otherwise.
5. Match the closure to the planned operation. Compare the runway named in the notice and the relevant date and time with the operation being considered.

These are distinct checks, not alternatives. Correctly decoding the time does not establish that the notice applies to the runway you intend to use. Correctly identifying the runway does not establish that the closure overlaps your planned operation.

Why Precise Pairing Matters Over Time

Airport activity, construction, and runway availability can change, and notices may express restrictions in different forms: a single interval, a recurring daily window, a partial-runway limit, or permanent decommissioning. As NOTAM information is presented through more search and display tools, the interpretive challenge remains stable: the runway identity and the effective time must stay linked.

That requirement has practical implications for both readers and interface designers. A useful presentation should make the designator and its schedule easy to inspect as a single operational statement, while retaining the underlying details needed to verify scope. For readers, familiarity with the date-time structure and schedule markers supports independent checking instead of reliance on a simplified summary alone.

References

1. https://web.archive.org/web/20220808013837id_/https://www.faa.gov/air_traffic/publications/atpubs/notam_html/chap3_section_3.html
2. https://web.archive.org/web/20220808014012id_/https://www.faa.gov/air_traffic/publications/atpubs/notam_html/chap5_section_1.html
3. https://web.archive.org/web/20220808002702id_/https://www.faa.gov/air_traffic/publications/atpubs/notam_html/appendix_a.html