Operation underway: Timeline of OceanGate’s missing Titanic tour submarine and the mission to save its crew

News of OceanGate Expedition’s missing submarine exploded on Monday as the U.S. and Canadian coast guards sprang into action with search and rescue missions.

Here is the timeline of how OceanGate’s Titan submersible went missing during its descent to the wreckage of the Titanic.

JUNE 17: U.K. billionaire Hamish Harding, one of the tourists aboard the missing sub, posts to Facebook one day before the sub is set to begin its descent.

“Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023,” Harding wrote “A weather window has just opened up and we are going to attempt a dive tomorrow. We started steaming from St. Johns, Newfoundland, Canada yesterday and are planning to start dive operations around 4am tomorrow morning. Until then we have a lot of preparations and briefings to do.”

LIVE UPDATES: SEARCH FOR OCEANGATE’S TITAN SUBMARINE 

JUNE 18: Harding boards the submersible alongside Pakistani businessman Shahzada Dawood, 48, and his son Sulaiman Dawood, 19. OceanGate CEO Stockton Rush also boards the submersible, as well as an OceanGate pilot whose identity has not been confirmed.

Critically, the crew are sealed into the vehicle with 17 bolts, and it cannot be opened from the inside. The craft has enough stored oxygen to keep the crew alive for 96 hours.

The Titan then departs the Polar Prince mothership Sunday morning and begins its descent over the wreckage of the Titanic. The ship loses contact with the submersible 1 hour and 45 minutes into the dive.

JUNE 19: At an unknown time, OceanGate sounds the alarm from the Polar Prince that the submersible has gone missing.

Immediately, the U.S. Coast Guard Northeast diverts a C-130 aircraft already in the area to begin searching the ocean surface. The Titan is designed to automatically surface in the event of a technical failure. If it is on the surface, rescuers must reach it within the 96-hour window to unseal the vehicle and release the crew.

Some failure may have caused the vehicle to remain stuck underwater. Rescue Coordination Center Halifax in Canada also delivers a P8-Poseidon aircraft, which is capable of dropping sonar buoys that can search underwater.

The U.S. and Canadian coast guards also dispatch more aircraft to the search area, located 900 miles off the U.S. northeast coast.

During this time, Harding’s stepson, Brian Szasz, confirms that Harding is on board the submersible in a statement on social media.

JUNE 20: Rescuers have been searching for roughly 48 hours and have covered 10,000 square miles of ocean, with no sign of the missing submersible.

Engro Corp. confirms that Dawood and his son are aboard the submersible in addition to Harding. OceanGate also confirms that CEO Rush is on board.

IMAGES SHOW OCEANGATE TITAN SUBMARINE’S FINAL MOMENT BEFORE IT BEGAN DIVE TO TITANIC 

“All that we know so far is that contact was lost with their submersible craft,” Engro wrote at the time. “There is limited information available beyond this that we know, and we humbly request that speculation and theorization is avoided.”

Meanwhile, rescue efforts are ongoing as the U.S. Coast Guard reaches out to both the U.S. Navy and the private sector for assistance. A commercial pipe-laying ship arrives to the area. Rescuers hope it will allow them to search depths of up to 3,800 meters after an unsuccessful night.

JUNE 20, 1 p.m. ET: The U.S. Coast Guard will offer an update on the latest rescue efforts.