Last week was quite a roller coaster for the airline industry across the globe. Following an Ethiopian Airlines Boeing 737 Max crash which killed all 157 passengers and crew members onboard, airlines around the world went ahead and grounded the plane citing safety issues. Now, while the investigation behind the crash is still ongoing, it has revealed some startling truth. Since the Boeing 737 Max is similar to the Boeing 737 itself, many pilots learned how to fly the plane on an iPad instead of a proper simulator.

Usually, when a new airplane goes into service, pilots undergo extensive training to get familiar with its software and how to fly it. This includes training on simulators that mimic the experience of flying the plane in the air. However, as the NYTimes report highlights, for the Boeing 737 Max, pilots who had prior experience flying a Boeing 737 learned about it on an iPad.

One key reason behind the lack of simulators for the 737 Max was that Boeing was still working on finalizing the engineering data of the plane right until it was nearing completion. Without the required engineering data, it was not possible to build a simulator for the Boeing 737 Max. Even now, months after the Boeing 737 Max went into service, there’s only one simulator designed for the plane available in the United States.

When United was set to take delivery of the 737 Max in 2017, a group of pilots put together training materials without ever flying the aircraft or a full simulator. James LaRosa, a 737 captain and union official who helped lead the training group, said he flew to a Boeing training center in Seattle to learn about the new plane on a mock cockpit that didn’t move like typical simulators.

In addition to a two-hour iPad training course from Boeing, he and colleagues used their experience in the cockpit to create a 13-page handbook on the differences between the Max and its predecessor, including changes to displays and the engines.

Like Boeing, the F.A.A. also believed that due to the similarities between the Boeing 737 and 737 Max, pilots flying the latter were not needed to go through additional simulator training. This has raised questions about many pilots not properly ready for the new software on the Boeing 737 Max which can be one of the reasons behind the crash.

The iPad material course did not talk about the new MCAS software in the Boeing 737 Max which has become a key talking point after the Lion Air crash.

Despite the F.A.A not requiring additional simulator training for the Boeing 737 Max, many airlines have gone ahead and ordered simulators for the plane. However, most of them are only going to receive their simulators by the end of this year, while others are looking at a waiting period lasting until 2020.