As US airports get busier, some are struggling to cope. Ageing technology and bad weather are often blamed for cancelled flights. But shortages of air-traffic controllers are also coming under widespread criticism in the media.
At Newark airport in New Jersey, hundreds of flights have been delayed or cancelled since the start of May. The Federal Aviation Administration (FAA) — which regulates aviation in the United States — says that 22 controllers are currently handling air traffic at Newark, considerably fewer than the 38 recommended by the agency (see go.nature.com/4mzavxw). Nationwide, only 2 out of 313 air-traffic facilities meet the staffing targets set by both the FAA and the union that represents controllers.
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Concerns about staffing levels have been raised since the mid-1980s. But, as demand grows, more planes require more air-traffic controllers to guide aircraft safely. The consequences of inadequate staffing levels are potentially serious. In June 2023, a US government report concluded that low numbers of staff pose “a risk to the continuity of air traffic operations” (see go.nature.com/4225jum).
FAA officials, union representatives and independent government watchdogs all propose just one solution: raise staffing levels. On 1 May, the FAA unveiled efforts to supercharge recruitment. By the end of the year, the agency expects to have hired at least 2,000 extra controllers — just 1,000 shy of its staffing target of at least 14,000.
However, having scrutinized how the FAA estimates staffing levels, there are reasons to question its assessment.
For one, the FAA ‘staffs to traffic’ — it bases staffing targets on forecasts of future flight volumes. The agency’s goal is to ensure that enough controllers are available to handle both peaks in air traffic and disruptions, such as bad weather.
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Yet, as a US National Academy of Sciences (NAS) report (see go.nature.com/43xanb5) notes, “FAA’s traffic forecasts, at least since 2000, have consistently overestimated future levels of air traffic.” In other words, the forecasts lead to a surplus — rather than a shortage — of controllers.
A more pressing concern is the mathematical model that the FAA uses to establish the staffing standard, which is defined as the number of controllers at each facility (of which there are more than 300) required to cover the 90th percentile of daily traffic (see go.nature.com/3tmacze). The model estimates, for each 15-minute period of the day, a controller’s ‘task load’, or the level of difficulty they encounter when doing the work.
The task load is assessed by scrutinizing the controller’s duties and calculating the time required to do them. A higher total indicates a higher, or more difficult, task load and thus requires more staff members. However, there are numerous problems with this approach.
Model estimates of the time needed for each task have not been validated using data from either the laboratory or functioning air-traffic control rooms. According to the NAS report, durations for seven of the nine tasks modelled by the FAA are “not based on data from the field”, whereas those for the remaining tasks are “based on input from subject matter experts—that is, task times are not derived from observing or analyzing controllers performing the tasks in the field or in experiments”. But if the loads are inaccurate, then so are the FAA’s modelled staffing requirements.
