TAMPA, Florida -- A SpaceX rocket on Sunday blasted off a powerful GPS satellite for the US Air Force, marking its 21st and final launch for the year.

A SpaceX mission control operator counted down to liftoff as the white Falcon 9 rocket took off under sunny, blue skies at 8:51 a.m. from Cape Canaveral, Florida.

The launch sent the Global Positioning System III space vehicle (SV) satellite into space to join the Air Force's constellation of 31 operational GPS satellites.

It promises "three times better accuracy" and an extended 15-year operational life, said a SpaceX statement.

Billions of people worldwide depend on GPS to support financial, transportation, and agricultural infrastructure.

SpaceX said the rocket was a "rare, expendable" version of the Falcon 9 since it would not attempt to re-land the booster after launch, needing to reserve all the rocket fuel to propel the satellite to its distant orbit.