SpaceX sent a packed rocket of 60 satellites into space on Thursday night, in a key first mission toward building the company’s own high-speed internet network.

The launch was "the heaviest payload a Falcon 9 [rocket] has ever launched, or Falcon Heavy, for that matter," SpaceX CEO Elon Musk told reporters before the mission. All in all, the rocket lifted more than 37,000 pounds of mass, he said.

Called "Starlink," the satellites represent the company’s ambitious plan to build an interconnected satellite network to beam high-speed internet to anywhere on the planet. It’s how Musk believes SpaceX will be able to generate enough revenue to realize its even more ambitious goals of sending astronauts to Mars, and to establish the first human colony on the Red Planet.

A Falcon 9 SpaceX rocket, with a payload of 60 satellites for SpaceX's Starlink broadband network, lifts off from Space Launch Complex 40 at the Cape Canaveral Air Force Station in Cape Canaveral, Fla., Thursday, May 23, 2019. John Raoux / AP

Starlink itself "is one of the hardest engineering projects I’ve ever seen done," Musk said.

The Falcon 9 rocket launched from the company's pad in Cape Canaveral, Florida. About an hour after liftoff, SpaceX deployed the 60 Starlink satellites in a "very low Earth orbit" of 440 kilometers above the surface.

The full Starlink network would consist of 11,943 satellites flying close to the planet, closer than the International Space Station.

Musk said SpaceX will need about 720 satellites in orbit to get "moderate" coverage around the world. Starlink will likely require several billions of dollars to fully develop but Musk said SpaceX has the funding needed to begin operations.

"At this point it looks like we have sufficient capital to get to an operational level," Musk said.

SpaceX is one of several companies, including Jeff Bezos’ Amazon, which are building these so called "constellations" of interconnected internet satellites.