SpaceX's reliable Falcon 9 space transportation fleet has been grounded after an unusual failure in its second stage caused its payload, 20 of the company's Starlink satellites, to deploy in a lower-than-expected orbit and eventually burn into the Earth's atmosphere.

In a statement on X, the social media platform formerly known as Twitter, the Falcon 9 in question launched Thursday (July 11) from its polar launch facility within Vandenberg Space Force Base in California, and its first stage successfully landed aboard a drone ship over the Pacific Ocean.

However, the company detailed that the Merlin Vacuum engine on the second stage "did not complete" its second of two scheduled burns, resulting in the Starlink satellites to deploy in a lower orbit than intended.

While the satellites attempted to raise their orbits using its built-in ion thrusters, SpaceX CEO Elon Musk said in a follow-up tweet that one of the five satellites that the company was able to contact disintegrated in the process of the thruster burn.

Eventually, the company said in its website that all of the Starlink satellites were considered lost given that the atmospheric drag neutralized the satellites' maximum available thrust.

Since the satellites were deployed in a lower-than-optimal orbit, they would not pose any threat to any operational satellite in orbit and would eventually burn up in the atmosphere in the next few days.

READ NEXT: Elon Musk's Starlink to Enter Telecoms Market of Sri Lanka After Changing Decades-Old Law

Falcon 9 Fleet Grounded due to FAA Investigation

CNBC reported that Falcon 9 launched 354 missions to orbit, with over 300 of them involving the successful return and landing of its first stage boosters, 280 of which were reflights after previous launches.

Space.com reported that this is the first time the rocket system experienced a major malfunction in its hardware since the 2015 launch failure involving the first version of its cargo Dragon capsule.

Since the Falcon 9 is human-rated, with a record spanning 13 crewed missions to date across four capsules, SpaceX and the Federal Aviation Administration (FAA) immediately initiated an investigation regarding the incident. This also meant that several SpaceX missions would also be delayed.

SpaceX is supposed to replace its four-person crew aboard the ISS with a fresh group in August, as well as replenish the station with a cargo Dragon mission. It would also supposedly provide support for the launch of the first of three Polaris missions sponsored by Shift4 Payments founder and CEO Jared Isaacman.

In a tweet regarding the failed Starlink mission, he insisted that he remained confident with the Falcon 9 system, saying that, from his personal experience flying aboard the Dragon capsule Resilience, SpaceX had an "incredible track record" with the Falcon 9. Isaacman previously went to space as commander of the all-civilian Inspiration4 fundraiser mission for St. Jude Children's Hospital in Memphis, Tennessee.

Another implication of the grounding is the crucial flight test of the beleaguered Boeing Starliner capsule currently docked to the International Space Station (ISS).

Supposedly only lasting a few days, NASA astronauts Barry Wilmore and Sunita Williams are still on board the station, causing speculations of them getting stranded in Earth orbit. With the grounding of the Falcon 9 and Dragon fleets, they would have to rely on the Starliner in the event that they needed to evacuate the ISS.

READ MORE: Elon Musk Offers Own Sperm to Colonize Mars - Is It Possible?