Live views of launch pad 39A (members only)

SpaceX called off a Falcon 9 countdown Wednesday due to the threat of lightning from thunderstorms along Florida’s Space Coast, pushing back the departure of a cargo mission for the International Space Station until Thursday.

Carrying a $2.7 billion NASA mission to Mars, a United Launch Alliance Atlas 5 rocket took off July 30 from Cape Canaveral and fired into a summer sky powered by four powerful solid rocket boosters and a kerosene-burning main engine.

On its third flight Monday night, SpaceX’s Falcon Heavy rocket will fly to three different orbits with two dozen spacecraft on a mission set to last more than six hours, prompting SpaceX founder Elon Musk to declare it the company’s “most difficult launch ever.”