The NTSB is calling on the U.S. Coast Guard to work with the Interior Department to mitigate methane discharges from offshore energy platforms in the Gulf of Mexico when helicopters are present. The recommendation follows two power-loss incidents in helicopters that led to accidents, one in 2011 and the other last year, on or near offshore oil platforms.

Methane ingestion can cause power surges, loss of power and engine flameouts in helicopters, the Safety Board said. In fact, the NTSB determined that the probable cause of the 2011 accident of a Bell 206L-3 was “the loss of engine power attributable to an engine compressor stall as a result of ingesting methane gas during takeoff.” The 2013 accident involved a Bell 407 and that probe continues.

The NTSB noted that as early as 2010 the Helicopter Safety Advisory Conference (HSAC) warned that single-engine turbine helicopters operating in the Gulf of Mexico often service platforms with helidecks near flare booms, exposing arriving and departing helicopters to gas discharges.