Provided the launch is successful, the Falcon 9 will try to land on a drone ship in the Pacific Ocean.
This was the company's 18th launch of a previously flown first stage.
While SpaceX still has a long way to go before Falcon 9 (or BFR) can hope to touch airliners, this triple launch and landing of a single Falcon 9 booster is the biggest step yet towards that critical goal.
A post on the official SpaceX Twitter account said the delay was necessary to "conduct additional inspections of the second stage".
This is the second delay for the launch.
"It includes 15 microsats and 49 cubesats from both commercial and government entities, of which more than 25 are from worldwide organizations from 17 countries, including the United States, Australia, Italy, Netherlands, Finland, South Korea, Spain, Switzerland, UK, Germany, Jordan, Kazakhstan, Thailand, Poland, Canada, Brazil and India", according to Spaceflight Industries.
A Falcon 9 launches to orbit for an unprecedented third time. One sponsored a balloon that will inflate in orbit and be visible from the ground.
As part of the mission, Spaceflight, a SpaceX customer, will send 64 small satellites for a ride on the rocket. The current record is held by an Indian rocket that launched 104 small satellites earlier this year. The 15 microsats and 49 cubesats be released into a "sun-synchronous low Earth orbit".
This will be the second largest rideshare mission ever and the largest for a single mission on United States soil.