147

THE COSTS OF BIRD STRIKES AND BIRD STRIKE 

PREVENTION 

JOHN R. ALLAN

Abstract: Collisions between birds (and other wildlife) and aircraft are known to cause substantial losses to the aviation industry 

in terms of damage and delays every year. Techniques exist to control bird numbers on airfields and hence to reduce the number 

of wildlife strikes, but they are applied at widely different levels from airport to airport. Some of this variation may be due to 

differing levels of strike-risk at the different sites, but much of it is due to the unwillingness or inability of the airports concerned 

to invest in bird strike prevention. Part of the reason for this reluctance to invest in airport bird control is a lack of understanding 

of the true costs to the airlines in terms of direct damage to aircraft and in delays and cancellations. Previous estimates of the 

cost of bird strikes have concentrated only on measurable repair costs and have not attempted to assign costs to aircraft delays. 

My paper uses newly available data from major international airlines to provide the first estimate for the total cost of bird strikes 

to the world’s airline fleet. Much of the data are commercially confidential and sources cannot be quoted nor the accuracy of 

the data verified. The estimates also rely on information from a very small number of airlines to produce extrapolations for the 

worldwide costs of damage and delays. Although these are major international carriers, and as representative as possible of the 

world bird strike problem as a whole, the results should be interpreted with a suitable level of caution. A tentative and probably 

conservative estimate of US$1.2 billion per year in damage and delays is the outcome of this calculation. The costs of bird damage 

are evaluated relative to the ability of managers to pay for bird control programs and the derived benefits thereof. Reasons for the 

industry’s failure to invest further to reduce the costs of bird strikes are examined.

Key Words: aircraft, airports, bird strikes, collisions, costs, economics, management, worldwide.

Collisions between birds and aircraft (bird 

strikes) can have catastrophic consequences and have 

resulted in the loss of at least 190 lives and 52 aircraft 

in civil aviation (Thorpe 1996). Military losses are 

more difficult to estimate, but there have been 283 

military aircraft lost and 141 deaths recorded in a limited number of western nations from which data are 

available between 1959 and 1999 (Richardson and West 

2000). The outcome of most bird strikes is far less 

severe, and the majority (65%) result in no damage to 

the aircraft at all (Milsom and Horton 1995). Those 

strikes that do damage aircraft or result in precautionary delays are an important cause of economic loss 

to the industry. To both preserve public safety and to 

reduce this loss as far as possible, the International Civil 

Aviation Authority (ICAO) recommends that airports 

should take steps to reduce the risk of bird strikes as 

far as reasonably possible. This recommendation may be 

reinforced by separate national regulations that require 

airports to take steps to reduce the bird strike risk (e.g., 

United Kingdom Civil Aviation Authority 1998). 

Bird strike prevention can be expensive and there 

has been no previous analysis of the costs and benefits 

it can bring to the aviation industry. Although the costs 

of bird control are easily determined, the costs of bird 

strikes to airlines are rarely collated in such a way 

that they can be separated from other operational costs 

(e.g., damage due to impacts with other objects such 

as debris on the runway etc.). Existing estimates of 

bird strike costs have relied on evaluating all of the 

bird strikes reported to a given nation; determining the 

levels of damage on a three-level scale (low, medium, 

severe); and then using the relatively small number 

of cases where damage costs are known to estimate 

an average cost for a given damage level (Cleary et 

al. 2000). This technique relies on assumptions being 

made about the number of unreported strikes and takes 

no account of the financial costs to the airlines of delays 

and cancellations resulting from aircraft needing safety 

checks or repairs following a bird strike incident.

Some airlines are now beginning to collate bird 

strike costs, and to determine the costs to the company 

of delays and cancellations. This has enabled an alternative approach to estimating bird strike costs to be undertaken. This technique uses actual costs to airlines of 

bird strike damage and uses accurately calculated cost 

data for delays and cancellations applied to the world 

airline fleet.

This revised approach allows the cost and benefits of additional investment in bird strike prevention 

to be calculated more accurately than has previously 

been possible. It also illustrates some of the problems 

inherent in a system where one commercial company 

(the airport) is spending money to allow another (the 

airline) to save on costs.

Many of the data presented throughout this paper 

are commercially confidential, and to obtain them it was 

necessary not to identify the companies from which 

they came. Additionally, it has been necessary to avoid 

presenting the data in such a way that the identity of the 

company could be inferred (e.g., by quoting an aircraft 

movement rate that would identify an airline). Some of 

the calculations undertaken are thus not presented in 

full, and none of the sources of previously unpublished 

information is identified. Although failing to attribute 
148

HUMAN CONFLICTS WITH WILDLIFE: ECONOMIC CONSIDERATIONS

sources of data is unusual, all data have been obtained 

from authoritative sources (e.g., company flight safety 

officers), and this is the only way that this paper could 

be produced. 

CURRENT ESTIMATES OF THE COST OF BIRD 

STRIKE DAMAGE

Reliable estimates of the cost of bird strikes to 

civil aviation are difficult to obtain, because of the failure of commercial airlines to collate bird strike damage 

data separately from other costs and because of the poor 

standard of reporting of bird strike incidents around 

the world. For example, Cleary et al. (2000) estimate 

that only 1 in 5 bird strikes in the United States is 

reported. It is impossible to determine whether the 

unreported strikes are those that result in no damage or 

whether damaging, and therefore costly, strikes are also 

unreported, and if so at what rate. Cleary et al. (2000) 

therefore provide minimum and maximum estimates for 

cost of damage and aircraft downtime in the United 

States. These range from 94,373 hours downtime and 

US$78.2 million in repair costs assuming that all damaging strikes are reported, to 471,867 hours downtime 

and US$391.4 million in repairs if only 1 in 5 damaging 

strikes is reported each year. 

Accurate estimates of damage costs are easier to 

obtain from military aviation. The U.S. Air Force (USAF) 

suffers around US$33 million per year in damage to 

aircraft (including aircraft losses) (USAF Bird Aircraft 

Strike Hazard Team personal communication) while the 

United Kingdom Royal Air Force (RAF) suffers around 

US$23.3 million in bird strike damage (excluding costs 

of lost aircraft) annually (RAF Inspectorate of Flight 

Safety personal communication). 

AN ALTERNATIVE APPROACH 

TO ESTIMATING COSTS

The cost calculation used here takes advantage 

of the fact that one major U.S. airline has a system 

that accurately tracks repair costs and flight delays due 

to bird strikes. The company is confident that its staff 

reports all bird strikes and the direct costs can thus be 

determined without concerns about failure to report. 

The disadvantage of this method is that it relies on a 

single company for a cost estimation, and, at present, 

data are only available for a single year. Thus, if the 

company concerned was fortunate enough to avoid any 

major bird strikes in that year then the estimate of 

damage costs will be artificially low. For example, a 

single incident that results in a total engine loss could 

incur a bill of US$5 million for a replacement engine. 

The presence or absence of 1 or 2 incidents of this 

nature could easily double or halve the total cost estimate for repairs. It would be preferable, therefore, to 

use data from several airlines for a period of several 

years, but this information is not yet available. 

The U.S. airline that supplied the cost figures 

for bird strikes assumes that, on average, each primary 

delay or cancellation (the delay or cancellation to the 

aircraft that was actually struck) results in 4 secondary 

delays or cancellations, either to subsequent flights to 

be made by that aircraft or to connecting flights that 

need to be held for passengers. The average costs 

of these delays and cancellations were obtained from 

another major U.S. carrier that has gathered the information in order to determine how both bird strikes 

and other sources of delay (e.g., failure of aircrew to 

report on time, air traffic control delays etc.) affect its 

business (Table 1). These figures are rounded estimates 

calculated for business planning purposes. Errors in 

these estimations may significantly affect the estimates 

of total cost (see below).

Table 1. Estimated costs of primary and secondary 

delays and cancellations to commercial transport aircraft (source major US airline).

Primary Delay US$75,000

Primary Cancellation US$75,000

Secondary Delay US$35,000

Secondary Cancellation US$75,000

Data for damage repair costs that do not require 

assumptions about reporting rates are therefore now 

available. By combining these with cost and frequency 

estimates for primary and secondary delays and cancellations, and dividing the total cost by the number of 

flights flown by the airline concerned, it is possible to 

calculate a cost per flight for bird strike damage. This 

cost can be extrapolated to any other airline, country, 

etc. where the air traffic movement rate is known. The 

one major assumption involved is that the rate of damaging bird strikes per flight is the same for the airline 

from which the cost data were obtained as it is for 

other airlines or countries around the world. The airline 

involved is one of the world’s largest and, although 

the majority of its operations are in the United States, 

it operates substantial numbers of flights around the 

world. It is thus one of the most representative samples 

of the world aviation business. The accuracy of the 

calculation would be improved if data from airlines 

that operate predominately outside the United States 

becomes available in the future.

The cost calculation presented here is restricted 

to the costs described above. There are other costs of 

bird strikes, such as increased insurance premiums for 

airlines and loss of passenger goodwill (and possibly 

repeat business) following significant delays. Other 

costs include the design of engines and aircraft to resist 

bird strike damage and the additional fuel costs and 

global pollution that result from stronger and heavier 
149

aircraft being developed to give additional bird strike 

resistance.

COST CALCULATION

The worldwide cost of bird strikes can be 

expressed mathematically as: n

((Σa+(75,000*b)+(75,000*c)+(75,000*4b)+(35,000*4c))ld)*e i

where 

a is the cost of damage repairs suffered by the 

airline supplying the cost data for each individual bird 

strike summed for the n incidents suffered in 1999.

b is the number of primary cancellations suffered 

in 1999 as a result of bird strikes by the airline supplying 

data.

c is the number of primary delays suffered in 1999 

as a result of bird strikes by the airline supplying data.

d is the number of air transport movements for 

the airline concerned.

e is the number of air transport movements for 

the world fleet.

Substituting values supplied by the airline, and 

using world Air Transport Movement (ATM) data from 

ICAO, the total cost of bird strikes for the world fleet is 

estimated at US$1,255,726,475 per year, which equates 

to US$64.50 per flight. 

The airline supplying information for this paper 

suffered a total of 1,326 bird strikes in 1999. The total 

cost of repairs resulting from bird strike damage was 

US$6,200,000 and the estimated total cost of delays and 

cancellations was US$46,450,000 making a total annual 

cost of US$52,650,000, or US$39,705 per bird strike 

event.

These estimates do not include helicopter traffic, 

nor the private aviation sector where smaller aircraft 

operating at lower speeds are involved. The costs of bird 

strikes to these aircraft may be different than costs for 

commercial airliners. The consequent costs in terms of 

delays and cancellations will also be substantially lower.

Assuming that the costs incurred by the airline 

supplying the information are typical of companies 

operating fixed-wing transport aircraft, then any airline 

can estimate the costs incurred for its organization 

simply by multiplying the total number of strikes experienced by US$39,705. Similarly, a national regulator can 

estimate the costs of bird strikes to transport aircraft 

in its territory by the same means. The accuracy of 

this cost calculation will, of course, depend upon the 

proportion of the bird strikes that have been reported. 

An alternative approach where reporting is thought to 

be unreliable would be to multiply the total number 

of ATMs for the country concerned by US$64.50 to 

arrive at a cost estimate independent of reporting rates. 

Any difference in the two estimates may give an indication of the level of non-reporting of bird strikes in the 

country or organization concerned.

LIMITS TO ACCURACY OF THE COST ESTIMATE

Because the data used to arrive at the cost estimates above are from such a small number of sources 

and cannot be independently verified, there is considerable scope for bias in the final result caused either by 

errors in the original data or by the fact that the data 

may not be representative of the industry as a whole. To 

better describe this possible bias the cost calculations 

have been repeated assuming a variation of plus or 

minus 10% in the annual total for damage costs and in 

the costs of delays and cancellations. The cost estimate 

has a range of US$1.27 to US$1.24 billion (a range of 

2.4% of the original US$1.25 billion estimate) if the 

cost of direct damage is varied by plus or minus 10%. 

If the estimated costs of delays and cancellations are 

varied by the same amount the cost estimate has a range 

of US$1.36 to US$1.14 billion (17.6%). Similarly, if the 

number of secondary delays and cancellations resulting 

from a primary delay or cancellation due to bird strike 

is varied by plus or minus 10%, i.e., from 3.6 to 4.4, 

the range in the resulting estimate of costs is US$1.18 

to US$1.33 billion (12% of the original estimate). This 

basic sensitivity analysis shows that it is the estimation 

of numbers of secondary delays and cancellations and 

the estimated cost of these that has the greatest effect 

on the final cost estimation. It is also here that the data 

are less certain, relying on company estimates which 

are not verifiable. Nevertheless, a world wide cost estimate for bird strike damage and delays of US$1 billion 

to US$1.5 billion per year for large transport aircraft 

remains the best estimate available.

EXISTING WILDLIFE MANAGEMENT OPTIONS 

FOR AIRPORTS AND THEIR COSTS

The basic premise underlying bird management 

on aerodromes is that reducing the number of birds 

present on and around the airfield will reduce the probability of a bird strike. The relationship between bird 

abundance and strike frequency is a complex one, however. At the national level, changes in bird numbers 

coincide with changes in strike frequency for those 

species where reliable data are available e.g., Canada 

geese (Branta canadensis) in the United States (Cleary 

et al. 2000), lapwings (Vanellus vanellus) in the United 

Kingdom (Bell 1999) and a variety of species of birds 

over 2 kg in weight (Allan et al. 1999). At the airport 

level, behavior of local populations of birds may have 

profound effects on the bird strike risk. For example, a 

change in the feeding location of one group of Canada 

geese that causes them to fly over the airfield could 

profoundly increase the strike risk at an airport without 

any change in total bird abundance. This may allow 

COSTS OF BIRD STRIKES AND BIRD STRIKE PREVENTION
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HUMAN CONFLICTS WITH WILDLIFE: ECONOMIC CONSIDERATIONS

an airport bird control program to target particular 

groups of birds that are increasing risk levels disproportionately, thus obtaining a greater benefit at reduced 

cost (Cooper 1991).

Bird management on airports usually seeks to 

modify the behavior of birds to reduce the numbers that 

come into the operating environment of the aircraft. 

The techniques used may involve the killing of some 

birds, but this is normally done to enhance the effectiveness of other techniques rather than to reduce total 

numbers in a local population. Conventionally, this bird 

control comprises 2 main elements: 1) habitat management to reduce the availability of resources such as food 

and water to the birds, and 2) active bird deterrence, 

either in the form of scaring devices or ‘bird patrols’ 

where airport staff or contractors actively deter or 

remove birds from sensitive areas using techniques such 

as pyrotechnics, recorded distress calls, or live ammunition. The most effective combination of techniques 

depends on the environmental conditions that prevail at 

the airport concerned and on the bird species that are 

causing the hazard. For example, Brough and Bridgman (1980) found that cultivating a dense grass sward 

15 to 20 cm long reduced numbers of gulls (Larus sp.) 

lapwings (Vanellus vanellus), golden plovers (Pluvialis 

apricaria), and starlings (Sturnus vulgaris) on airfields 

in Great Britain by up to 75% compared to short grass 

(5- to 10-cm) swards. In contrast, 15- to 20-cm grass 

swards in areas where large birds of prey are abundant 

may cause significant problems because they can support large populations of small mammals, which attract 

raptors and owls (J-L Briot personal communication, 

Barras 2000). Whatever the techniques employed, largescale habitat management on airfields is likely to involve 

significant costs, and the deployment of staff and/or 

equipment for bird scaring is a further ongoing cost to 

the airport operator.

The maintenance of bird-repellent grass swards of 

the type used in the United Kingdom involves regular 

cutting of the grass, removal of cuttings once a year 

and applications of fertilizers, selective herbicides, and 

occasionally, insecticides (Mead and Carter 1973, UK 

CAA 1998). The frequency of cutting and the need 

for chemical treatments varies from site to site, but 

typical costs range from US$80,000 to US$250,000 per 

year (RAF Strike Command personal communication). 

In an effort to reduce chemicals and the costs of maintenance, alternative poor, long grass swards have been 

developed in some countries. These involve reducing 

the nutrient status of the soil to reduce grass growth 

and hence lower cutting frequency as well as encouraging a diverse flora by eliminating the use of herbicides 

and insecticides. Such methods would reduce the cost 

of maintenance considerably (to around US$5,000 to 

US$10,000 per year) (Dekker 2000), but their effectiveness compared to the more expensive regime has not 

been rigorously tested. 

Elsewhere in the world, different habitat management regimes are employed. For example, in desert 

environments, where cultivating grass swards is impossible, the airfield is simply rolled flat and no vegetation 

is permitted to grow. This results in little or no bird 

attraction. Airfields situated in swampy habitats rely on 

drainage or netting of wetland areas to deter shorebirds 

or fish-eating species that are the main hazards at these 

sites (Bird Strike Committee Europe 1990). Unfortunately, data on the costs of these activities are rarely 

available.

As well as managing the airfield habitat, many 

airports need to manage other features to make them 

unattractive to birds. Examples include bird-proofing 

buildings to deny access to birds such as house sparrows (Passer domesticus) or feral pigeons (Columba 

livia), or modifying amenity plantings to remove trees 

or bushes that offer roosting or nesting sites to birds. 

The costs of these operations vary depending on the 

nature and scope of the works involved.

In summary, it is likely that an effective habitat 

management regime (i.e., one which has a significant 

effect on the numbers of birds using the airfield or 

its surroundings) might cost an airport in the region 

US$75,000 per year to implement in Western Europe. 

The different management techniques and differences 

in labor costs in other parts of the world might significantly alter these figures.

The second element of airfield bird control, active 

bird control, can be similarly difficult to cost. On most 

civil airports, the bird control staff is part of the operations or fire departments which have duties other than 

bird control. Few airports separate the costs of their 

bird management programs from the other functions of 

the departments concerned and separate costings are 

thus difficult to obtain. Some airports, however, employ 

contractors to provide bird control services and in these 

cases the costs of the services are readily available. In 

the United Kingdom, the RAF employs contractors at 

almost all of its airfields. Annual costs vary between 

US$130,000 for 24-hour bird control involving continuous patrolling, bird dispersal, and wildlife depredation 

services on a fast jet station, and US$65,000 for patrolling between 9 a.m. and 5 p.m. At a training station 

(RAF Strike Command personal communication). In 

the United States, costs of bird control programs vary 

between US$25,000 for a basic harassment program 

conducted by military staff to US$150,000 per year for a 

full bird control program involving falconry (R. Dolbeer 

personal communication).

Airports also need to influence the types of development that occur close to their property in case these 

attract birds. In some countries, the types of develop-
151

ment that are allowed near airports are restricted (e.g., 

landfills might be prohibited within a certain distance), 

while in others, airports are given the opportunity to 

object to bird-attracting developments close to the site. 

The costs of evaluating developments close to airports 

can be considerable, requiring the use of expert consultants, and if a legal dispute results, costs can become 

very high indeed. Even if the airport is successful in 

preventing a development without resorting to legal 

action, there will be opportunity costs to the developer 

whose application has been denied.

THE COST EFFECTIVENESS OF EXISTING BIRD 

STRIKE PREVENTION MEASURES

Milsom and Horton (1995) showed that, where a 

bird control program was already in place at an airport, 

increased investment was only effective in reducing the 

number of bird strikes if it resulted in a specified level 

of bird control efficiency score. The way that this score 

was derived was not precisely defined, but it required 

the implementation of standard bird repellent grass, 

the provision of bird control equipment in the form of 

pyrotechnics and distress calls, staff who had attended 

a recognized training course and a specified level of 

staff presence on the airfield (T.P. Milsom, personal 

communication). Based on estimates provided by the 

RAF, this level of bird control and habitat management 

would cost around US$200,000 per year per airfield to 

implement in the United Kingdom. Less expensive programs may have significant benefits in situations where 

bird control is minimal or absent, or where investment 

can be made in large-scale reductions in bird populations close to airports. For example, the implementation 

of even the most basic bird scaring at an airport with 

large numbers of large birds such as geese on or close 

to the runway would significantly reduce the risk of a 

costly strike. 

One example of the costs and benefits of a substantial bird control program is available from John 

F. Kennedy International Airport (JFK) in the United 

States. Prior to the introduction of improved control 

techniques, the airport suffered an average of 300 

strikes per year (Dolbeer 1998) which based on the 

calculation above, would have cost the airlines that used 

the airport a total of around US$12 million each year. To 

combat the problem, the airport implemented a habitat 

management policy, hired a full-time wildlife biologist, 

employed a team of shooters to kill gulls flying over the 

property during the main risk period and recruited a 

bird control company specializing in falconry to assist 

the airport operations staff who carry out routine bird 

dispersal duties throughout the year. Although there 

is some debate about the relative effectiveness of the 

different components of the new bird management program (Dolbeer 1998), the implementation of shooting 

alone reduced the number of strikes from around 170 

per year to around 50 per year during the period that 

the shooting teams were in place (Dolbeer et al. 1993, 

Dolbeer and Chipman 1999). The 120 strikes thus prevented would have cost the airlines using the airport 

US$4,764,600 each year, compared to the cost of the 

shooting programme which was US$120,000 per year 

(R.A. Dolbeer personal communication).

THE POTENTIAL COSTS AND BENEFITS 

OF FURTHER INVESTMENT 

IN AIRPORT WILDLIFE MANAGEMENT

To determine whether additional investment in 

bird management would result in significant savings, the 

costs of the bird strikes that would be prevented must 

be determined. If the strikes that are prevented carry 

the average cost of US$39,705 calculated above, then 

it would require only a reduction of 5 strikes to cover 

the total costs of a program of the sort required to 

reach Milsom and Horton’s bird control efficiency score 

of 75%. Similarly, the example quoted from JFK airport 

above resulted in a save:spend ratio of 39:1. Unfortunately, the organizations required to invest in the additional control (the airports) are not those that benefit 

from the reduced bird strike costs (the airlines).

There are a number of options available to link 

the costs and benefits of investment in bird strike prevention. One would be for airports to increase the landing fees charged to airlines by a small amount per flight 

and to invest this money in improved bird control. Providing that data could be gathered to show that the 

increased investment had paid dividends in terms of a 

reduction in bird strikes, it may be possible to persuade 

the airlines that a small increase in landing fees is an 

acceptable price to pay for improved safety and reduced 

damage and delays. An alternative approach would be 

for national regulators to require a certain level of bird 

control in the same way that other safety features such 

as fire and emergency services are required at a certain 

level for a particular category of airport. At present, 

some nations (e.g., the United States, Canada, Australia, 

and most European countries) have some level of formal 

inspection of bird control practices, such as an annual 

audit by a regulator. Only France has formal requirements for a specified level of bird control provision 

for airports of different sizes. In the developing world, 

many airports have no bird control requirement, and 

hence no bird control. It is at these airports where 

airlines have the greatest potential to invest money in 

bird control, which would result in a net benefit by producing a greater savings in reduced bird strike damage 

and delays. Assisting airports in the developing world 

with the development of even elementary bird control 

programs where none existed before could substantially 

reduce the bird strike frequency suffered by the airlines 

COSTS OF BIRD STRIKES AND BIRD STRIKE PREVENTION
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HUMAN CONFLICTS WITH WILDLIFE: ECONOMIC CONSIDERATIONS

that operate there. In countries where labor costs are 

low, the prevention of 1 average bird strike might be 

sufficient to pay for an entire year’s bird control program. Given that airports with no bird control are likely 

to suffer from a greater proportion of costly strikes 

by large and/or flocking birds (those that would be 

dispersed first if properly targeted bird control was in 

place), the potential savings provided by this investment would be even greater. The converse of this argument applies to those airports with sophisticated and 

expensive bird control programs already in place. At 

these sites, the number of strikes by large birds or 

flocks should be lower and the majority of bird strikes 

will be with small non-damaging bird species. The benefits of investing in improved bird control at these sites 

may thus be lower, but at present there are insufficient 

airport-specific data on bird strike costs to allow this 

hypothesis to be tested.

COSTS OF DESIGNING AIRCRAFT 

TO WITHSTAND BIRD STRIKES

Many aircraft components are required to pass a 

bird-impact test before being allowed into service. The 

test is designed so that the probability of a catastrophic 

accident following the failure of the system or component is less than 1 in every 109

 flying hours. An engine, 

for example, might have to demonstrate the ability to 

provide a certain level of power for a specified period 

of time following an impact with a given number of 

birds of a given weight. When these certification tests 

are designed, a calculation is undertaken which evaluates the frequency of strikes with a particular size and 

number of birds, the probability of an engine losing 

power after hitting a bird of this size, and the probability of that power loss leading to a crash. Effective 

bird control can have a profound effect on that calculation. If airport bird controllers target the large bird species and flocks of birds that are more likely to cause 

damage (Milsom and Horton 1995), the probability of 

a catastrophic power loss is reduced. When calculating 

the need for a particular level of certification test, regulators set a target of no more than 1 catastrophic incident in 109

 flying hours as an acceptable level of safety. 

If bird strikes with the most hazardous species can 

be reduced in frequency to the point where the risk 

of catastrophe is lower than this threshold, then more 

stringent certification tests may be avoided and the need 

to design additional robustness into an engine may be 

eliminated. The stronger the engine, the heavier and 

less fuel-efficient it becomes. This not only increases the 

fuel costs to the operator, but also increases the levels of 

pollutant gasses discharged into the upper atmosphere 

by aircraft. Such gases are known to contribute to global 

warming, the costs of which are beyond the scope of 

this paper to estimate.

CONCLUSION

The estimate of US$1.2 billion per year for 

damage and delays to commercial transport aircraft 

caused by bird strikes is probably conservative and 

should be interpreted with caution as the data which 

underlie it are limited, and the assumptions made to 

arrive at the final figure are considerable. As airlines collect more data and differentiate bird strikes from other 

foreign-object damage, it will be possible to produce a 

more refined analysis. This will permit the separation 

of different bird species, airlines, and airports to better 

identify the costs and benefits involved in bird strike 

prevention. Nevertheless, it is clear that a substantial 

amount of the annual cost of bird strikes could be saved 

if properly targeted investment in bird strike prevention 

is made in the future. In the intensely competitive air 

travel industry, the key is to connect the savings due to 

reductions in bird strike costs with the investment in 

airport bird control. It will also be necessary to develop 

methods to gather the data needed to evaluate the true 

cost effectiveness of increasing bird control provision 

and of the existing bird strike measures currently in 

place at airports.

ACKNOWLEDGMENTS

This work was supported by the Central Science 

Laboratory of the United Kingdom Ministry of Agriculture Fisheries and Food. My particular thanks are due to 

those members of the aviation industry, most of whom 

requested to remain anonymous, who took the time and 

trouble to collate and supply the data used in this paper 

and to the airlines and other companies involved who 

allowed them to release the information. Two anonymous referees made very helpful comments on the original manuscript.

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COSTS OF BIRD STRIKES AND BIRD STRIKE PREVENTION