The National Transportation Safety Board (NTSB) is cautioning on the dangers of dust devils, saying they have been present in more than 170 aircraft accidents it has investigated since 1982.

Noting that dust whirlwinds are often considered a harmless phenomenon, the Safety Board highlighted their hazards to aviation, detailing related accidents involving small fixed-wing aircraft and rotorcraft.

“For pilots unfamiliar with or inattentive to the presence of dust devils, especially when operating at low altitudes, the consequences can be catastrophic,” the agency said in a safety alert, Dust Devils: Silent Sky Snares.

Dust devils can occur under clear skies and warm conditions, forming in areas of strong surface heating, NTSB noted, adding that they can be as strong as tornadoes and waterspouts. “Given their often invisible nature (unless they pick up dust and debris), dust devils pose a risk of sudden and unexpected turbulence for pilots and aircraft, which may lead to rapid loss of lift, uncommanded roll or yaw, or other disturbances,” the Safety Board said.

The NTSB cited related accidents, including a Grumman G-164B Ag Cat that flew through a dust devil after taking off from a dirt airstrip in Saffell, Arkansas. It subsequently lost lift and crashed into a field inverted with substantial damage.

In another instance, an MD-369FF helicopter flew into a dust devil shortly after takeoff in Palm Gardens, Nevada. The encounter caused a sudden right yaw, loss of lift, and an uncontrollable hop, the NTSB said. “The pilot attempted to maintain control during the descent but the main rotor struck the tailboom, which sustained substantial damage; the skid gear was also damaged.”

The NTSB provided guidance on detecting dust devils, noting that they can cast a shadow on the ground. “Even if the dust devil doesn’t have visible debris, the vortex itself can cause enough air density and temperature differences to create a visible shadow.” Further, dust devils can leave tracks on the ground, even if they don’t lift debris, the Safety Board added.

“Always be vigilant for the potential presence of dust devils, especially in regions known for them, such as the U.S. Southwest,” the Safety Board advised. “Scan areas thoroughly before takeoff and landing, as well as during low-level flight operations. If operating in areas known for frequent dust devil activity, maintain a higher altitude, when possible, to minimize the encounter risk.”

The NTSB stressed that pilots should not assume visibility equals safety. “Just because a dust devil is not picking up debris doesn’t mean it’s not there.” Additionally, the agency urged pilots to be informed and on the lookout for their potential in weather briefings. Further, if a pilot suspects having flown through one, they should inspect their aircraft.