Following weeks of delays, a planned 150-meter flight of SpaceX’s Starhopper test vehicle was aborted literally in the last second shortly after 6 p.m. Monday at the end of a nail-biting countdown to T-0.

SpaceX’s YouTube live feed announced shortly before 7 p.m. that no further launch attempt would be made Monday, though another attempt could take place today.

Cameron County has authorized closures for Boca Chica Beach and State Highway 4 from the beach to Oklahoma Avenue from 2 p.m. to midnight today and Wednesday, alternative launch dates for the launch of Starhopper.

Elon Musk, the company’s CEO, indicated via Twitter that the problem was with the Starhopper’s ignition system. Monday’s flight was to have been a follow-up to Starhopper’s 60-foot hop on July 25. SpaceX had planned for the vehicle to reach 200 meters on its second flight, though the launch permit issued Aug. 23 by the Federal Aviation Administration specified that the flight not exceed 150 meters in altitude.

The FAA had issued a Notice to Airmen (NOTAM) for Aug. 26-28, 2 p.m. to midnight each day, prohibiting aircraft operation within four miles of the launch site from ground level up to and including 8,000 feet above sea level.

On Aug. 24, residents of Boca Chica Village, 1.5 miles west of the launch site, received hand-delivered alerts recommending that they evacuate the area before the scheduled hop in the event of an “overpressure event” caused by a malfunction during flight that could cause windows to break.

“At a minimum, you must exit your home or structure and be outside of any building on your property when you hear the police sirens which will be activated at the time of the Space Flight Activity,” read the advisory.

Overpressure results from atmospheric pressure being pushed to a higher-than-normal level due to a shockwave from an explosion or sonic boom. Cameron County Judge Eddie Treviño Jr. said Monday morning that the alerts were distributed to residents at the request of the FAA.

“If we hadn’t provided any notice and God forbid something happened, we’d be in a different situation,” he said. “We’d rather err on the side of caution.”

SpaceX broke ground at the Boca Chica site in September 2014. The first static engine fire tests on Starhopper took place in early April, and the first untethered “hop” on July 25. Once it takes place, the 150-meter (500-foot) hop will be Starhopper’s second and final flight, according to Musk.