A SpaceX Falcon 9 rocket launches the Inmarsat-5 F4 communications satellite into space from Pad 39A of NASA's Kennedy Space Center in Cape Canaveral, Florida on May 15, 2017.

CAPE CANAVERAL, Fla. — A SpaceX Falcon 9 rocket lifted off from launch pad 39A at NASA's Kennedy Space Center here today (May 15) with a communications satellite that will complete Inmarsat's fifth-generation broadband network.

The 23-story-tall booster soared off its seaside launch pad, which once hosted NASA's space shuttles and Apollo moon rockets, at 7:21 p.m. EDT (2321 GMT). It was the sixth of more than 20 missions SpaceX plans to fly this year.

Perched on top of the two-stage rocket was the 13,400-lb. (6,100 kilograms) Inmarsat-5 F4 communications satellite, the heaviest spacecraft yet to be delivered by a Falcon booster into a geostationary transfer orbit some 22,300 miles (35,800 km) above Earth. [Photos: SpaceX Launches Inmarsat-5 F4 Satellite]

A SpaceX Falcon 9 rocket launches the Inmarsat-5 F4 communications satellite into space from Pad 39A of NASA's Kennedy Space Center in Cape Canaveral, Florida on May 15, 2017. (Image credit: SpaceX)

The satellite separated from the Falcon 9's second stage right on time, about 32 minutes after liftoff.

"It's been a great afternoon and evening," said SpaceX mission commentator John Insprucker. "All you can ask for today."

Getting F4 into its intended orbit emptied the Falcon's fuel tanks, leaving no propellant for the booster's first stage to attempt a landing on either a drone barge or the ground.

The Falcon 9 rocket and Inmarsat-5 F4 satellite continue to climb into the Florida skies on May 15, 2017. (Image credit: SpaceX)

So far, 10 Falcon 9 first stages have returned intact after launching, including one rocket that has now flown twice. SpaceX plans to launch a second used rocket next month for satellite operator Bulgaria Sat.

Inmarsat, which is flying for the first time with SpaceX, had hoped to have its $250 million F4 satellite in orbit last year, but the flight was delayed after a Falcon 9 exploded on the launch pad as it was being fueled for a preflight engine test on Sept. 1.

The delay cost SpaceX a second launch contract with London-based Inmarsat, which instead hired European competitor Arianespace for a mission now slated to fly in late June aboard an Ariane 5 rocket.

SpaceX, which has now flown the Falcon 9 six times successfully since the launch pad accident, has a backlog of more than 70 missions, worth more than $10 billion. Inmarsat has an option for another future flight with SpaceX.

Inmarsat-5 F4 completes the company's four-member, $1.6 billion broadband satellite constellation called Global Xpress, which provides global, mobile communications for airlines, ships, government agencies and other customers.

The fifth-generation satellites, which were built by Boeing, provide downlink communication speeds of up to 50 megabits per second and uplink speeds of up to 5 megabits per second for customers on land, at sea or in the air, Inmarsat said in a press release. That speed is about 100 times faster than Inmarsat's previous-generation system provided.

Customers for the Global Xpress' inflight Wi-Fi services include Lufthansa Group and Austrian Airlines.

The previous three satellites in the network were launched aboard Russian Proton rockets in 2013 and 2015.

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