With both computers and human controllers cautiously watching every single rocket function, it's not unusual for SpaceX to abort a launch. However, yesterday a Falcon 9 rocket was stopped at literally the last second, confusing even the countdown commentator. As the clock hit zero, the operator enthusiastically shouted "Liftoff!" but quickly added "Disregard. We have an abort" once it was clear the rocket wasn't getting airborne.
Apparently, the launch was aborted automatically by the Falcon 9's onboard computer after it detected a Merlin 1D engine issue. During the commentary, SpaceX supervisor Michael Andrews noted that it had a "condition regarding engine power that caused us to abort today's launch." SpaceX later added, via a tweet: "Standing down today; standard auto-abort triggered due to out-of-family data during engine power check." The company said it would reveal the next launch date "once confirmed on the range."
The launch would have marked the first time a Falcon 9 main booster has been used five times. The company also reused a payload fairing from a previous mission. SpaceX was planning to launch 60 more of its Starlink satellites designed to bring low-cost internet to far-flung places. The sytem should be operational soon, but has been controversial because the highly reflective satellites have been marring astronomical observations.