Apollo 13 was supposed to land in the lunar region of Fra Mauro, but this landing site was later reassigned to Apollo 14.

At 46 hours, 43 minutes mission elapsed time, Joe Kerwin, the CAPCOM on duty, said, "The spacecraft is in real good shape as far as we are concerned. We're bored to tears down here." Nine hours, 12 minutes later, a Service Module oxygen tank blew up aboard Apollo 13. The Command Module's normal supply of electricity, light and water was lost, and they were about 321,869 kilometers (200,000 miles) from Earth.

James Lovell Jr. gasped, "Hey Houston, we've had a problem here." While looking outside, Lovell reported to Houston, "We are venting something out into the- into space". Jack Lousma, the CAPCOM replied, "Roger, we copy you venting." Lovell said, "It's a gas of some sort." It was oxygen gas escaping at a high rate from the second, and last, oxygen tank.

A formidable task ahead for both crew and ground control, plans now changed. The crew moved to the Lunar Module to escape the decreasing air pressure in the Service Module. The crew had to conserve food and water. To get around the Moon and then go home, the Lunar and Command Modules needed to conserve fuel.

Due to debris from the explosion, the navigation system was unreliable. The crew used the Sun as a navigation point to guide the crippled craft back to Earth. While enduring discomfort and little sleep, the crew moved back into the cold Command Module, then ejected both the Lunar and Service Modules. After re-entry, the crew landed safely in the Pacific Ocean almost four days after the explosion.