Air India pilot’s reported cannabis test: What it can and can’t tell investigators

In August, an Air India Airbus A320 lost around 300 feet of altitude during a flight from Phuket to Delhi, injuring 13 passengers and four crew members. The aircraft, carrying 137 passengers and eight crew, landed safely in Delhi. Both pilots were undergoing post-flight screening for psychoactive substances. The captain's initial test required confirmatory testing, and both pilots were temporarily removed from flying duties pending further investigation. However, Air India has not confirmed the captain's alleged cannabis positive result.

The reports have sparked controversy over pilot drug testing and aviation safety in India. While a positive cannabis test might seem like damning evidence, it does not necessarily implicate the pilot in the incident. The effects of cannabis on a pilot's performance can be complex and difficult to determine.

Research suggests that cannabis can impair fine motor control, attention, and complex human-machine interaction, which are crucial in flying. Studies conducted on pilots who smoked marijuana showed significant deterioration in several measures, including altitude, heading, radio navigation, elevator and aileron control, landing accuracy, and approach performance. Importantly, some pilots did not realize their performance had worsened.

However, the link between a positive cannabis test and impairment at the time of the incident is not straightforward. The effects of cannabis can vary depending on factors such as the dose, method of consumption, frequency of use, and individual biology. A positive test can indicate that THC is present, but it cannot definitively determine when the substance was consumed or whether the pilot was impaired at the time.

Furthermore, THC can remain detectable in the bloodstream for days or even weeks after last use, particularly in frequent users, even when acute impairment has subsided.

In summary, while a positive cannabis test may raise questions about a pilot's state of mind, it does not automatically implicate them in an incident. The science behind cannabis and its effects on aviation performance is still evolving, and more research is needed to better understand the relationship between cannabis use and pilot impairment.