By Aeruxo — Licensed Flight Dispatcher | 15+ Years in Airline Operations
The braking action report came in seven minutes before our aircraft
was on final approach: “POOR. Runway 14L. Reported by B737 at 1423Z.”
I pulled up the landing distance calculation immediately. Our aircraft
needed 1,840 metres to stop under normal conditions. The published
landing distance on a runway with poor braking action applies a
multiplier that pushed the required distance to 2,650 metres. Runway
14L was 2,800 metres long. That left 150 metres of margin between a
normal landing and a runway excursion. I called the crew with the
numbers and flagged the alternate. The captain elected to hold for
15 minutes and request an updated braking action report from the
next landing aircraft. The updated report came back “MEDIUM.” The
aircraft landed without incident and stopped with 400 metres remaining.
Those numbers are why I do not treat contaminated runway reports as
routine information.
A runway excursion—a term that encompasses both overruns past the
end of the runway and veer-offs to the side—is consistently among the
most frequent categories of aviation accident worldwide, yet it is
one of the least discussed among passengers. The reason is partly
that many runway excursions involve no fatalities and minimal aircraft
damage, and therefore generate little news coverage relative to
in-flight emergencies. But the serious variants—high-speed overruns
on short or contaminated runways—are among the most consequential
events in commercial aviation safety statistics. After 15 years
calculating landing distances and monitoring braking action reports,
I want to explain exactly what causes a runway excursion, what the
systems designed to prevent and arrest them actually do, and what the
numbers behind the threat really mean.
Arresting System) bed after a runway excursion overrun. The crushable
concrete arrested the aircraft’s movement without structural
catastrophe. EMAS exists specifically because some runway excursions
cannot be prevented—only mitigated.
Key Takeaways
- A runway excursion occurs when an aircraft departs
the runway surface laterally (veer-off) or longitudinally
(overrun) during landing, takeoff, or rejected takeoff.
It is the most statistically common category of serious aviation
accident worldwide. - The three primary causes are landing long, excessive
speed at touchdown, and inadequate braking action—often
in combination with a contaminated runway surface. - Landing distance calculations are not estimates.
They are certified performance numbers that account for specific
atmospheric, surface, and aircraft conditions. Dispatchers
calculate and crews verify these numbers before every landing. - EMAS (Engineered Materials Arresting System)
is the engineered last line of defence beyond the runway end—
crushable concrete that absorbs aircraft energy and stops an
overrunning aircraft without structural catastrophe. - Most runway excursions are survivable when
they occur at reduced speed on airports with adequate Runway End
Safety Areas. Speed at excursion is the single most critical
variable in outcome severity.
This article is based on real operational experience coordinating emergency scenarios in an airline Operations Control Center (OCC).
1. What a Runway Excursion Actually Is
The ICAO definition of a runway excursion covers two distinct
events that share a common outcome. An overrun
occurs when an aircraft cannot stop within the available runway
length and departs the far end—most commonly during landing, but
also possible during a rejected takeoff (RTO) where the crew aborts
the takeoff run and cannot stop before the runway end. A
veer-off occurs when an aircraft departs the side of the
runway—during landing, takeoff roll, or RTO—typically caused by
asymmetric braking, crosswind exceeding directional control limits,
a tire failure, or nose gear steering anomaly.
The severity of a runway excursion depends almost entirely on
what lies beyond the runway surface. An excursion onto a flat,
dry grass safety area at low speed produces minimal damage and no
injuries. An excursion at high speed into terrain, drainage
structures, or airport perimeter infrastructure produces outcomes
of a different order entirely. Modern runway safety standards
mandate a Runway End Safety Area (RESA) extending at least 90
metres beyond the runway end, and 240 metres at certificated
international airports—but the installed safety area at legacy
airports with constrained geometry is not always adequate for
the aircraft types operating there. This gap is what EMAS was
engineered to address.
2. The Three Root Causes of a Runway Excursion
friction available for braking. The thrust reversers help but cannot
substitute for wheel braking on a runway where the tyre-surface
friction coefficient has dropped to a fraction of its dry value.
Landing long—touching down beyond the intended touchdown
zone—is the most common contributing factor in landing
overrun runway excursions. The touchdown zone on a standard ILS
approach is the first 300 to 600 metres of the runway. An aircraft
that floats during the flare and touches down 600 metres past the
threshold has effectively shortened its available stopping distance
by 600 metres before a single brake has been applied. On a 2,800-metre
runway with a required landing distance of 2,400 metres, a 600-metre
long landing eliminates the entire safety margin in a single moment.
Unstabilised approaches—where the aircraft is too fast, too high,
or incorrectly configured at the stabilisation gate—are the primary
cause of long landings, which is why stabilisation criteria are among
the most strictly monitored parameters in commercial aviation flight
data monitoring programs.
Excessive speed at touchdown compounds the
landing-long scenario and also acts as an independent cause. Aircraft
stopping distance scales with the square of speed—an aircraft
touching down at 155 knots instead of the calculated 140 knots has
23 percent more kinetic energy to dissipate, requiring proportionally
more runway. On a dry runway with adequate stopping distance this
excess is manageable. On a contaminated runway where braking
performance is already degraded, the same speed excess can push
the required distance beyond the available distance entirely.
Contaminated runway surface is the third and most
operationally variable cause—the factor I monitor most closely from
the dispatch desk. Ice, compacted snow, slush, standing water, and
rubber deposits from previous landings all reduce the friction
coefficient that wheel braking depends on, and each produces a
different degradation profile that the landing distance calculation
must account for.
3. How Landing Distance Is Actually Calculated
The landing distance published in the aircraft’s performance manual
is the certified stopping distance under a defined set of conditions:
sea level, standard atmosphere, dry runway, maximum braking, specified
approach speed, and a 50-foot threshold crossing height. In practice,
no landing occurs under all of these conditions simultaneously, so
the calculation incorporates factors for actual conditions: airport
elevation, temperature, aircraft weight, wind component, runway slope,
and runway surface state. The result is an actual required landing
distance that is specific to the flight, the aircraft, and the
conditions reported at the time of the approach.
Runway condition is reported through a standardized system.
The Global Reporting Format (GRF), implemented across ICAO member
states from 2021, uses Runway Condition Codes (RWYCC) from 6 (dry)
to 0 (nil braking action) to standardize the way pilots and
dispatchers interpret braking action reports. Each code corresponds
to a landing distance factor—a multiplier applied to the dry
landing distance to give the contaminated runway required landing
distance. A RWYCC of 1 (near the minimum) applies a multiplier of
approximately 1.70, meaning the aircraft needs 70 percent more
runway than on a dry surface. According to the
FAA Runway Excursion Risk Reduction
guidance, inadequate understanding and application of runway
condition reports is a documented contributing factor in a
significant proportion of runway excursion events—which is why the
standardization to GRF was a priority safety initiative.
within the first seconds after touchdown to achieve certified stopping
performance. Delay in either system—or a failure to deploy—directly
reduces the stopping margin and increases runway excursion risk.
4. EMAS: The Last Line of Defence Against a Runway Excursion
blocks arranged to progressively absorb landing gear energy as an
overrunning aircraft’s wheels sink in. The system arrests the
aircraft without the catastrophic deceleration that terrain or
hard structures produce.
EMAS (Engineered Materials Arresting System) is installed at the
ends of runways where the standard Runway End Safety Area cannot meet
minimum length requirements—typically at airports where terrain,
roads, water, or airport boundaries constrain the area beyond the
runway threshold. The system consists of blocks of crushable cellular
concrete arranged in a bed of increasing depth beyond the runway end.
When an overrunning aircraft’s landing gear enters the bed, the blocks
crush progressively under the wheel loads, absorbing kinetic energy
and decelerating the aircraft over the length of the bed without
the abrupt deceleration that a hard barrier or terrain feature would
produce. The aircraft stops; the landing gear sinks into the crushed
material; the fuselage remains level and structurally intact.
EMAS has successfully arrested several aircraft in real runway
excursion events since its introduction, most notably at airports
where conventional safety areas were too short to stop an overrunning
aircraft on their own. The system is not universal—installation cost
and the specific geometry of each runway end determine where it is
deployed—but it represents a meaningful safety upgrade at constrained
airports where a runway excursion into the area beyond the conventional
RESA would otherwise be catastrophic. According to
SKYbrary’s runway excursion
reference, the outcome severity of runway excursions correlates
most strongly with the speed at which the aircraft exits the runway
surface and the nature of what it encounters immediately beyond—
making the RESA and EMAS the two highest-leverage infrastructure
interventions available.
5. What the Dispatcher Does About Runway Excursion Risk
remarks—I cross-reference every contaminated runway report against
the aircraft’s certified landing distance for the conditions before
releasing the flight. The margin is the number that determines
whether I release, hold, or re-route.
Runway excursion risk assessment is one of the most concrete and
numerical parts of my daily work. For every flight releasing to a
destination with a reported or forecast contaminated runway, I run
the landing distance calculation against the available runway length
and verify the margin. The calculation uses the aircraft’s current
landing weight (fuel burned at arrival), the destination’s reported
RWYCC, the forecast wind at arrival time, the runway elevation and
slope, and the specific autobrake setting the airline’s procedures
specify for the conditions. The resulting required landing distance
must fit within the available runway length with the applicable
margin—typically 15 percent on a wet runway for dispatch purposes—
or the flight does not release to that destination without an
alternate plan.
When margins are tight, I have three levers. Routing to
a longer runway at the same airport is the simplest—many
airports have multiple runway lengths, and a 500-metre difference
in available runway can transform a marginal calculation into a
comfortable one. Delaying departure to allow runway
conditions to improve—either through snow clearing
operations or temperature rise—is the second option when conditions
are borderline and forecast to improve within the holding fuel
window. Loading additional alternate fuel to support
a divert if arrival conditions have deteriorated is the third—this
does not reduce the runway excursion risk at the destination but
ensures the crew has a safe alternative rather than being committed
to an approach in conditions that are beyond the aircraft’s certified
performance. For how contaminated runway conditions interact with
my broader winter operations planning, my
flying in snow and ice article covers the full winter weather
dispatch sequence.
6. What Passengers Should Know About Runway Excursions
most common and least serious type of runway excursion—the aircraft
stops intact, passengers disembark normally, and the investigation
focuses on the directional control anomaly rather than survivability.
A firm, fast-stopping landing is not a rough landing—it
is a safe one. On a short or contaminated runway, the crew
may select maximum autobrake, apply full reverse thrust immediately
at touchdown, and hold the brakes aggressively throughout the
rollout. This produces a noticeably firm stop that can feel abrupt
compared to the smooth arrivals passengers prefer. It is the correct
technique—certified stopping performance requires that specific
brake and reverse sequence to be achieved, and a gentle landing
with delayed braking on a contaminated runway is the scenario that
produces runway excursions, not prevents them.
If you are on a short or snow-covered runway, the crew
has already done the calculation. The numbers on my desk
and on the crew’s performance chart account for the conditions
outside the window. The flight was released to that destination
because the calculation showed an adequate margin. If the reported
conditions deteriorated after release, the crew received the updated
braking action report on approach and made their own go or no-go
assessment before crossing the threshold. A go-around executed at
low altitude over a short runway in poor conditions is one of the
least comfortable passenger experiences—and one of the most correct
crew decisions. For how go-around decisions are made and what they
feel like from the cabin, my
go-around article explains the full decision chain.
Keep the seatbelt fastened through the entire landing
roll. Runway excursions that occur at low speed—after most
of the energy has been dissipated—are highly survivable when
occupants are restrained. The deceleration loads during a runway
excursion, even onto grass or soft ground, can throw an unrestrained
passenger forward against the seat ahead or into the overhead
compartment. The seatbelt sign remains illuminated through the
landing roll specifically because the rollout, not just the
touchdown, is a phase where structural events can occur.
Frequently Asked Questions
What is a runway excursion?
A runway excursion is any event in which an aircraft departs the
runway surface during landing, takeoff, or rejected takeoff. It
encompasses overruns (departing the far end of the runway) and
veer-offs (departing the side). Runway excursions range from low-speed
grass excursions with no damage or injury to high-speed overruns
into terrain or structures with serious consequences. It is
consistently one of the most statistically frequent categories of
serious aviation accident in global data.
What causes most runway excursions?
The primary causes are landing long past the intended touchdown
zone, excessive approach or touchdown speed, and contaminated runway
surfaces that reduce braking friction below the values used in the
landing distance calculation. These factors frequently combine—an
unstabilised approach producing a long, fast touchdown on a
contaminated runway creates a runway excursion risk that no amount
of post-touchdown braking can fully compensate for. Directional
control failures causing veer-offs are a separate category involving
crosswind, asymmetric braking, tire failure, or nose gear anomaly.
What is EMAS and how does it stop a plane?
EMAS (Engineered Materials Arresting System) is a bed of crushable
cellular concrete blocks installed beyond the runway end at airports
where the standard Runway End Safety Area is too short. When an
overrunning aircraft’s landing gear enters the bed, the blocks
crush progressively under the wheel loads, absorbing kinetic energy
and decelerating the aircraft without the abrupt deceleration that
terrain or hard structures would produce. The aircraft stops with
the fuselage intact and the landing gear embedded in the crushed
material.
How does the dispatcher assess runway excursion risk?
Before every flight releasing to a destination with a reported
or forecast contaminated runway, the dispatcher calculates the
required landing distance for the specific conditions—aircraft
weight, runway condition code, wind, elevation, and slope—and
verifies it fits within the available runway length with the
required margin. If the margin is insufficient, options include
routing to a longer runway, delaying for conditions to improve,
or loading additional fuel to support a divert. The calculation
is repeated if updated braking action reports arrive during the
flight.
Can a rejected takeoff cause a runway excursion?
Yes. A rejected takeoff (RTO) initiated at high speed requires
the aircraft to decelerate from near-rotation speed to a full stop
within the remaining runway length. The Accelerate-Stop Distance
(ASD) certification ensures that a correctly executed RTO at or
below V1 (the decision speed) can be accomplished within the
available runway, but an RTO initiated above V1, a late recognition
of the reject condition, or degraded braking performance on a
contaminated runway can all result in an overrun excursion. High-speed
RTOs that progress to runway excursions are among the most serious
categories because the aircraft carries its full fuel load at speed.
What is a Runway End Safety Area (RESA)?
A Runway End Safety Area is the graded, obstacle-free area beyond
the runway threshold designed to reduce the risk of damage to an
aircraft during an overrun. ICAO standards require a minimum RESA of
90 metres beyond the runway end for instrument runways, and 240 metres
at certificated international airports. The RESA is graded to support
the weight of the aircraft type without causing excessive damage and
is kept clear of obstacles. Where the required RESA length cannot be
achieved due to terrain or infrastructure, EMAS can be installed to
provide equivalent arrest capability.
Is a runway excursion always catastrophic?
No. Most runway excursions involve low speeds at the point of
runway departure and result in minimal or no aircraft damage and no
passenger injuries. The severity depends primarily on the speed at
excursion and what the aircraft encounters beyond the runway edge or
end. A low-speed veer-off onto a flat grass safety area is a
reportable incident; a high-speed overrun into an embankment or
drainage ditch at 80 knots is a major accident. The runway safety
infrastructure—RESA, EMAS, obstacle-free zones—exists specifically
to convert potential high-severity outcomes into survivable ones by
controlling what lies beyond the runway surface.
Have you experienced a landing that felt unusually firm or
a rollout that seemed longer or faster than normal? Share what you
noticed in the comments—passenger observations of stopping
performance help others understand what different runway conditions
actually feel like from the cabin.
Disclaimer: The views expressed in this article are my own
professional opinions based on 15+ years of operational experience.
They do not represent the official position of any airline, aviation
authority, or regulatory body.
Licensed Flight Dispatcher with 15+ years of experience in airline operations control. Holds FAA Aircraft Dispatcher Certificate and Republic of Korea Flight Dispatcher License (MOLIT). Specializes in flight watch, NOTAM analysis, flight planning, and operational control at a Korean LCC. IOSA audit participant and author of multiple airline operational manuals, including Emergency Response, De-icing, and OCC Procedures.