WASHINGTON — With thunderstorms bearing down on Wallops Island, Va., Orbital Sciences Corp. said it would wait until April 20 to make its second attempt to launch the Antares rocket on its long-awaited test flight.

An April 17 launch attempt was aborted 10 minutes before liftoff when a data cable connecting the Antares’ upper stage to the rocket’s mobile launch tower came loose. Orbital blamed the premature disconnect on a combination of slight hydraulic movement of the so-called Transporter Erector Launcher and not enough slack left in the data cable to allow for the unplanned movement. 

“The good news is that this is a simple adjustment to the external support system,” Frank Culbertson, Orbital executive vice president and mission director for the Antares test flight, said in a statement. “Given that this is a first run for the rocket and the first time use of a new launch facility, the fact that all systems were performing as planned while the team proceeded through the pre-launch checklists is very encouraging.”  

Orbital initially planned to try again April 19 but the weather outlooked prompted the Dulles, Va.-based company to shoot for a 5:00 p.m. EDT liftoff on April 20 instead. Orbital has a second opportunity April 21.