Here's a summary of the latest developments:

• Human remains and aircraft seats are among the debris found floating in the Mediterranean Sea
• Search teams are combing the waters in an area with a 65km (40 mile) radius
• An oil slick has been spotted by satellite, but there is no confirmation that it has come from the EgyptAir plane

• It remains unclear why the plane crashed
• Here is our main story 
• You can read a summary of what we know so far about MS804
• You can also keep up to date with our coverage on BBC TV and radio.  

The brother of a Welshman on board the crashed EgyptAir flight says the last two days have been "overwhelming" as the family await more news.

Former British Airways pilot Eric Moody says that EgyptAir flight MS804 may have turned off its flight route to avoid descending into "something coming the other way."

The brother of a Welshman on board the crashed EgyptAir flight describes him as a role model with a warm heart.

The search operation in the Mediterranean will need to be extended for every hour that it continues, according to a maritime security expert.

Ioannis Chapsos, a research fellow at Coventry University, has written a piece for The Conversation, external on the difficulties facing the MS804 search and recovery crews.

He writes: "An aircraft that crashes on land may end up in inaccessible areas such as tropical forests or mountain peaks, but it will remain at the same location. 

"At sea, however, the additional dimension of depth makes the rescue teams’ efforts extremely hard.

"As time passes by, sea currents and weather conditions will cause wreckage to drift. 

"In practice, this means the search and rescue area must continue to expand for every hour the search goes on."

The Vatican says the pope has conveyed his solidarity to Egypt's president and the families of the victims, AP reports.

The Vatican's secretary of state said in a message to President Abdel-Fattah el-Sissi that Pope Francis "wishes to assure you of his prayers and solidarity at this difficult time". 

The Pope also offered "divine blessings of strength and peace" to the relatives of the passengers and those involved in the search operations.

One flight MS804 passenger almost did not make the trip after losing his passport last week, only for it to be found on the street days later, his friends say.

Safwat Moslem, the chairman of EgyptAir, says the current search area has a 65km (40 mile) radius, but it will be expanded if necessary. 

Image source, bbc

The Egyptian navy says it has found more wreckage from the MS804, including human remains, luggage and passengers' seats.

Earlier today, an Egyptian military spokesperson said wreckage and passengers' belongings had been found 290km (180 miles) north of Alexandria.

In a statement, Egypt's civil aviation ministry said: "The Egyptian navy was able to retrieve more debris from the plane, some of the passengers' belongings, human remains, and plane seats. The search is ongoing."

Image source, AP

The BBC has discovered that the EgyptAir plane that disappeared yesterday had previously made an emergency landing at Cairo airport.

On 25 June 2013, en route from Cairo to Istanbul, as the aircraft was climbing to 24,000 feet, the pilot noticed that the number one engine was overheating.

He decided to turn the aeroplane round and fly it back to Cairo. The official report, external (in Arabic) says a technical defect was found in the engine and was repaired. 

The UK's Foreign Secretary, Philip Hammond, has tweeted his support to the family of Richard Osman, the Welsh geologist who was on board MS804.  

Associated Press

The passenger manifest for MS804 contained no known names on current terror watch lists, three European security officials have said, according to the Associated Press news agency, external.

The lists are often used by both European and US security and law enforcement agencies, said the officials, who spoke on condition of anonymity because they were not authorised to comment on the ongoing investigation, AP reports.

Former British Airways pilot Eric Moody has spoken to the BBC about why MS804 reportedly made two sharp turns before dropping more than 25,000ft (7,620m) and plunging into the sea.

Mr Moody said the sudden 90 degree turn, the first sharp maneuver recorded by military radar, may have been the pilot turning out of the airway - a kind of pathway planes stick to. 

"You would turn off because you wouldn’t want to descend ... in case you descended into something coming the other way," he said.

“I would think then something happened and it went totally out of control.”

Earlier the BBC, and others, reported on an apparent 12 minute gap in the air traffic control log between a failed attempt to contact the aircraft and it disappearing from radar.

But the Greek ATC timeline reported by news agencies appears to have been wrong. 

A statement from the Greece's aviation authority (HCAA) says the gap between the first failed attempt to contact the aircraft and it dropping off radar was two minutes 40 seconds.

Here's the full timeline published by the HCAA:

• Egypt Air flight MSR 804, A320 en route from Paris to Cairo entered ATHINAI FIR at 02:24 am local time. It was Radar identified and cleared by the competent Air Traffic Controller for the flight path.

• At 02:48 am local time, the flight was transferred to the next Area Control Center Sector and was cleared by the ATC for the exit point of ATHINAI FIR. The pilot was jocund and thanked in Greek.

• At 03:27 am local time, ATHINAI Area Control Center tried to communicate with the flight for transfer of communication and control from ATHINAI FIR to CAIRO FIR.

• Despite the repetitive calls, the flight did not respond and thus the Air Traffic Controller called on the emergency frequency without response.

• At 03:29 am local time the flight was over the boundary point, between ATHINAI and CAIRO FIRs.

• At 03:29:40 am local time the flight signal was lost from radar, almost 7 NM south/southeast from KUMBI point (boundary point, between ATHINAI and CAIRO FIRs), within Cairo FIR.

• Immediate assistance of the Hellenic Air Force radars was requested for possible target tracking, with no avail.

• At 03:45 am local time Search and Rescue (SAR) operations were activated through JRCC (Joint Rescue Coordination Center), NAOP (National Air Operations Center) and ADIC (Air Defense Information Center), while updating the Egyptian Civil Aviation Authorities.  

Image source, EPA

UK Foreign Secretary Philip Hammond has pledged continued support for the ongoing search for wreckage of the MS804. 

He said: "We have offered the Egyptian government any support that it requires in searching for wreckage, in analysing anything that is found. 

"So far we haven't had any requests but I will be speaking to my Egyptian counterpart in just a few minutes' time."

The BBC's Middle East correspondent, Lina Sinjab, who is in Cairo, says some families have already carried out funerals with empty coffins for their loved ones.

She said: "The rituals here are they have to bury the dead as soon as they die, but they are in a really difficult position because they don't know if the bodies would ever arrive, so they're still waiting at the moment. 

"They did this as a symbolic move to commemorate their lost ones."  

The European Space Agency (ESA) says one of its satellites has detected what appears to be a 2km-long oil slick in the eastern Mediterranean Sea – in the same area that Flight MS804 disappeared.

The ESA said it had given information related to the image to the authorities involved in the search.

The agency has been scrutinising satellite data since the aircraft vanished, looking for any clues as to why and where it went down.

According to the satellite image, the slick was at 33°32' N / 29°13' E – about 40 km southeast of the last known location of the aircraft. 

Osman Abu Laban, a Cairo-based Lebanese film director, has posted on his Facebook, external page to say that he lost four members of his family in the crash - his uncle, aunt, cousin and his cousin's wife.  

He posted pictures of the family members and a message praying that they would find peace.

Image source, Facebook

Image source, Reuters

US Secretary of State John Kerry has told his Egyptian counterpart Sameh Shoukry that the US will continue to support the investigation and search for Flight MS804.

The State Department said Mr Kerry offered Mr Shoukry condolences for the lives lost in the plane crash and promised to stay in close contact as the investigation progresses.

Oceanographer Dr Simon Boxall tells the BBC that Flight MS804 went down in a very difficult part of the Mediterranean to search.

"I think the assumption is that this is a shallow water area but it's not, this part of the Mediterranean is really quite deep," he said.

"We only have limited information about the crash location, but if it is where this debris has been found then it sits on a boundary where the ocean floor is more like the Alps, very rugged and contoured.

"That area borders a large, deep plain about 3km down."

Dr Boxall said an aircraft such as the A320 could easily "slip through the cracks" of the ocean floor in the area.

"This is a very soft sediment area and wreckage could sink very quickly, so they need to find it fast," he said.

The ocean floor ridges could also act to block signals from the black box pinger, and sonar from vessels searching for the wreckage, he said.

"Having thought this was a relatively simple one, it could actually be very difficult."