BBC News 21 June 2023
- The US Coast Guard has confirmed that a Canadian P-3 aircraft detected "underwater noises" in a search area for the missing Titanic sub
- US media, citing internal US government memos, described them as "banging sounds"
- Contact with the miniature sub, which has five people on board, was lost on Sunday as it made a 3,800m descent to the Titanic wreck
- The sub's air supply is expected to run out on Thursday, at around 11:00 BST (10:00 GMT)
- On board is British-Pakistani businessman Shahzada Dawood and his son Suleman, along with British explorer Hamish Harding
- Paul-Henry Nargeolet, a former French Navy diver, is also on the vessel, as is Stockton Rush, chief executive of OceanGate - the firm behind the dive
- US court documents show an expert warned of safety problems in the sub in 2018, before he left his job at OceanGate
On the surface:
The sub might be able to alert rescuers if it can reach the surface through radio transmitters and GPS signals. It has strobe lights and radar reflectors to help the rescue teams spot them.
But locating the sub may be hard, especially from the air because it's white in colour. Changeable weather and poor visibility will also pose a challenge to the teams.
Underwater:
Rescuers must also comb depths that could reach nearly 4km (2.5 miles) to look for the craft, which is 6.7m (22ft) long. The US Coast Guard has extended the search into deeper waters.
Radio and GPS signals can't travel through water, so the only other way to detect the sub is through sonar and sonar buoys, often used in hunting for enemy submarines.
They work by detecting movements and sounds in the water - like the one the US Coast Guard reported - or by bouncing a sonar "ping" off the surface of the vessel (active detection) and listening for the returning echo.
Read more about how the teams are locating the sub here.
