About 15 months ago, aviation regulators grounded the Boeing 737 MAX after it was involved in two fatal crashes within a short period of mere five months. The grounding has subsequently been extended multiple times as new issues were uncovered. However, on Monday, the 737 MAX took to the skies again, which is a major step for the airline manufacturer. The Federal Aviation Administration (FAA) is working with Boeing to re-certify the 737 MAX.

Monday's test flight lasted several hours. To ensure that the 737 MAX is safe to fly again, Boeing and the FAA will execute a wide array of flight maneuvers as well as emergency procedures during the test flights.

If all goes well, the 737 MAX could soon be flying commercial flights, though nobody knows for sure when that can and will happen. Flight data from the test flights will be carefully reviewed and analyzed over a couple of weeks, and extra steps in the re-certification process also have to be completed before the 737 MAX can be cleared to return to the skies.

While re-certification with the FAA is one step, there are other issues that Boeing will have to deal with. 737 MAX airline operators will need to retrain their pilots, and Boeing will also have to make the critical updates to all its 737 MAX planes around the world.

Boeing is conducting the test flights over a period of three days this week, with the first one already held on Monday. There is no definite timeline and the process is likely to take several more months.

Aviation authorities in several regions around the world have already made clear they plan to carry out their own assessments regarding the suitability of the 737 MAX aircraft's return to service rather than take the FAA's word.

Adam Luehrs is a contributing writer at GET.com based in California. He likes traveling to new and exciting destinations, preferably on his credit card company's dime. When not on the road, Adam enjoys hiking around the mountains of San Diego, trying out new food and reading history books. Email: adam.luehrs@get.com.