Boeing has completed a patch for anti-stall software linked to deadly crashes of its 737 MAX, the company said Thursday, bringing the grounded jet a step closer to resuming commercial flights.

The modification has been checked in a variety of simulations, and the 737 MAX has also completed engineering test flights, the Chicago-based planemaker said in a statement. Boeing is now giving the Federal Aviation Administration additional information on how pilots use the aircraft’s controls and displays in a variety of scenarios and will work with regulators to schedule a certification flight.