Some airlines are reportedly flying Boeing 737 Max models despite the months-long grounding order from global regulators. While some industry experts questioned the legality of the matter, there could be a good reason for moving the planes.

According to Simple Flying, there are several reasons why some airlines are forced to fly the embattled jets even if all fleets have been grounded worldwide since March. It is also worth noting that there are no passengers riding the planes while they are moved.

One of the supposed reasons why some airlines need to fly the grounded jets is due to high fees in some international airports. For instance, the London Heathrow airport charges high fees so most airlines don't allow their planes to sit at the said airport for a long time.

Another issue is the location. Ever since the Boeing 737 Max jets were grounded, some planes were stranded in high humidity or stormy regions. To cut down on further losses and expenses, airlines with stranded jets in regions with harsh weather conditions need to ask permission to move the planes.

Finally, some stranded Boeing 737 jets need to be flown and moved to a different location from where they are grounded for maintenance checks, especially with the new MCAS upgrade.

Before a Boeing 737, Max jet is moved, airlines reportedly make sure an expert pilot will board the plane. It is also speculated that the trained and briefed pilot is accompanied by an official with the U.S. jet maker to ensure safety and control in case of emergency.

While safety measures may be taken during the flight of a grounded jet, some industry analysts questioned the legality and safety of the pilot or pilots onboard. After all, the Boeing 737 Max jet has yet to be cleared of safety issues following the tragic crashes in October 2018 and March.

Safety concerns were triggered further after it was revealed that Boeing executives allegedly rejected a particular safety system and opted for a more affordable one. A senior engineer with the company reportedly filed a complaint earlier this month due to the issue.

Federal investigators are also looking into how the U.S. Federal Aviation Administration (FAA) certified the jets in question amid the latest revelations surrounding proper safety measures.

Furthermore, Southwest Airlines pilots indicated that the grounded planes may not be allowed to fly until February - a far cry from the supposed recertification in August that was hampered by continued skepticism from regulators.

The FAA has yet to confirm when it will recertify the troubled Boeing 737 Max jets.