Multiple sources of data are essential in assessing avia-
tion safety. Confidential surveys of pilots and other
crew members provide insights into perceptions of
organisational commitment to safety, appropriate
teamwork and leadership, and error.3 Examples of sur-
vey results can clarify their importance. Attitudes about
the appropriateness of juniors speaking up when
problems are observed and leaders soliciting and
accepting inputs help define the safety climate.
Attitudes about the flying job and personal capabilities
define pilots’ professional culture. Overwhelmingly,
pilots like their work and are proud of their profession.
However, their professional culture shows a negative
component in denying personal vulnerability. Most of
the 30 000 pilots surveyed report that their decision
making is as good in emergencies as under normal
conditions, that they can leave behind personal
problems, and that they perform effectively when
fatigued.2 Such inaccurate self perceptions can lead to
overconfidence in difficult situations.
A second data source consists of non-punitive inci-
dent reporting systems. These provide insights about
conditions that induce errors and the errors that result.
The United States, Britain, and other countries have
national aviation incident reporting systems that
remove identifying information about organisations
and respondents and allow data to be shared. In the
United States, aviation safety action programmes
permit pilots to report incidents to their own
companies without fear of reprisal, allowing immediate
corrective action.5 Because incident reports are volun-
tary, however, they don’t provide data on base rates of
risk and error.
A third data source has been under development
over 15 years by our project (www.psy.utexas.edu/psy/
helmreich/nasaut.htm). It is an observational method-
ology, the line operations safety audit (LOSA), which
uses expert observers in the cockpit during normal
flights to record threats to safety, errors and their
management, and behaviours identified as critical in
preventing accidents. Confidential data have been col-
lected on more than 3500 domestic and international
airline flights—an approach supported by the Federal
Aviation Administration and the International Civil
Aviation Organisation.6
The results of the line operations safety audit con-
firm that threat and error are ubiquitous in the aviation
environment, with an average of two threats and two
errors observed per flight.7 The box shows the major
sources of threat observed and the five categories of
error empirically identified; fig 1 shows the relative fre-
quency of each category. This error classification is
useful because different interventions are required to
mitigate different types of error.
Proficiency errors suggest the need for technical
training, whereas communications and decision errors
call for team training. Procedural errors may result
from human limitations or from inadequate proce-
dures that need to be changed. Violations can stem
from a culture of non-compliance, perceptions of
invulnerability, or poor procedures. That more than
half of observed errors were violations was unexpected.
This lack of compliance is a source of concern that has
triggered internal reviews of procedures and organisa-
tional cultures. Figure 1 also shows the percentage of
errors that were classified as consequential—that is,
those errors resulting in undesired aircraft states such
as near misses, navigational deviation, or other error.
Although the percentage of proficiency and decision
errors is low, they have a higher probability of being
consequential.7
Even
non-consequential errors
increase risk: teams that violate procedures are 1.4
times more likely to commit other types of errors.8