The Boeing 737 MAX aircraft, which were earlier grounded after two deadly crashes, could be brought back to service, according to Boeing’s chief executive officer.

Boeing’s CEO Dennis Muilenburg, at an investor conference in California, was reported as saying that, “I think a phased ungrounding of the airplane among regulators from around the world is a possibility.”

The aircraft has been grounded since mid-March after two fatal crashes that killed all 346 people on board. Boeing has cut production of the 737 MAX from 52 to 42 per month as well. The company may reduce production again or temporarily halt it, depending on the scenario.

The company is working with the US Federal Aviation Administration (FAA) and other regulators to bring back the Boeing 727 MAX back to service by the end of the year.

The European Union Aviation Safety Agency (EASA) revealed that it will allow the Boeing 727 MAX aircraft to fly only after Boeing meets four critical conditions.

Firstly, the changes made by Boeing to these aircraft would have to be approved by the agency. Secondly, the agency will carry out a broader review of the design of the critical safety systems on these flights, which was earlier done by the FAA.

Thirdly, the EASA needs to have a clear and detailed understanding of the two accidents and lastly, Boeing must adequately train its flight crews with regard to the changes being made to the aircraft’s software.

In 2013, Boeing’s 787 Dreamliner was grounded for several months after four aircraft suffered from electrical system problems caused by its batteries. However, aviation authorities around the globe later agreed to allow the aircraft to fly again.