Aircraft manufacturers and safety officials are collaborating to develop a secure emergency oxygen system, following a move by FAA this year to remove them from aircraft lavatories.

FAA said the development of the systems will take two to four years to complete; safety advocates and flight attendants feel that is not fast enough. Serious injuries or fatalities could result in the event of decompression at higher altitudes, they claim.

FAA, the Transportation Security Administration (TSA) and the FBI removed the oxygen generators, saying the generators could have been easily fabricated, creating a flight hazard. The agencies say the move was entirely precautionary. FAA says safety officials are working as quickly as possible to outfit systems for all U.S. operated passenger aircraft.