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TEM Description

TEM serves as the primary measure for LOSA observation. Developed by members of The LOSA Collaborative in the late 1990s, TEM is a conceptual framework that suggests threats, errors, and undesired states are critical events that frontline workers must manage to maintain adequate safety and efficiency margins.


TEM’s fundamental premise relies on the notion that frontline workers can be better trained and supported to anticipate, detect, and recover from threats, errors, and undesired states.

While LOSA observation of TEM performance is comprehensive, the areas of focus can be viewed as three general categories: threats, errors and undesired states.


Observable events or errors that occur outside the influence of a frontline worker requiring immediate attention to manage safely. Examples of threats include frontline workers having to manage weather, aircraft malfunctions, challenging ATC clearances, or errors that come from other departments.


Observable frontline worker deviations from organizational or individual expectations or intentions. Examples of errors include making a wrong automation entry, not turning on a system for protection, missing a checklist item, or failing to brief a critical item.

Undesired States

Observable states induced by a frontline worker that exhibit an apparent reduction in safety margins. Examples of undesired states include speed, vertical, or lateral aircraft deviations with an increased potential for an incident or accident.

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