With weekend vigils planned for the passengers of missing Air France flight 447, Brazilian and French officials remained at odds Friday about what clues and remnants of the missing jetliner lie in the Atlantic Ocean.
Heavy rain and poor visibility today is complicating the search for the plane the missing Air France flight that vanished Sunday with 228 people onboard. It is the latest setback in the increasingly daunting search for the missing jetliner some 700 miles off Brazil's coast.
On Thursday night, Brazil's military announced that despite earlier reports to the contrary, pieces of debris pulled out of the ocean Thursday were not from the missing plane. Brazil authorities still believe they have located parts of the plane -- including a 23-foot chunk of plane, an airline seat and several large brown and yellow pieces that likely came from inside the plane, military officials said -- but they have not pulled them out of the ocean.
"French authorities have been saying for several days that we have to be extremely prudent," countered France's Transportation Minister Dominique Bussereau on France's RTL radio Friday. "Our planes and naval ships have seen nothing."
The confusion calls into question whether any of the debris searchers have spotted from the air is from the missing aircraft.
A team of searchers Thursday had picked up what appeared to be standard airplane emergency equipment, a cargo pallet and two buoys, and initial reports suggested the items might have been from the crashed plane.
But later, Brazilian military officials said debris recovered so far some 400 miles from Brazil's Fernando de Noronha islands was not from the missing Airbus. For one thing, the plane was not carrying wooden luggage pallets, The Associated Press reported.
"No material from the flight was removed," Brazilian Air Force Gen. Ramon Cardoso said. "What we saw was debris that belonged to some aircraft that were left behind because we have a priority on the search [for] bodies. But so far, no piece of the aircraft has been found."
Ceremonies for the passengers on flight 447 get underway in France this weekend, including an international Sunday service at Notre-Dame Cathedral in Paris. Another service will be held Saturday at Roissy-en-France church, a diocese that had four people on board the flight, according to Air France.
The memorials come as France this weekend sends additional high-tech equipment to help hunt for clues. A French nuclear submarine that can travel underwater at 25 knots is on the way to help search for the plane's black boxes, and is expected to arrive on site next week. Also on the way is a French search and exploration ship carrying robots that can plunge about 20,000 feet underwater to help recover wreckage.
Air France Flight 447: Airbus Sends Out Alert on Plane Speed
There is no clear explanation why Air France Flight 447 vanished en route from Rio de Janeiro to Paris.
Federal police in Rio said they have confirmed that all passengers on the flight have been checked as part of an effort to rule out terrorism.
French Foreign Minister Bernard Kouchner did not categorically rule out terrorism as a cause when speaking to reporters last night. "Nothing leads us to believe that there was an explosion, but that doesn't mean there wasn't one. Once again, all the paths are open and we will not give priority to a single premise because that would be immoral."
One factor in the accident may have been the speed of the plane.
According to a memo obtained by the Associated Press, Air France is replacing instruments in some of its Airbus planes that gauge airspeed. The development reported by the AP comes on the heels of an alert released Thursday by Airbus, saying the automated maintenance messages coming from the flight "indicate that there was inconsistency between the different measured airspeeds."
"Therefore and without prejudging the final outcome of the investigation, the data available leads Airbus to remind operators what are the applicable operational recommendations in case of unreliable airspeed indication," the Airbus statement read.
Though it's too early to know for sure, the memo suggests the systems that tell the computers how fast the plane was flying may not have all been working properly.
Today an Airbus expert told ABC News that even if planes are receiving inconsistent airspeed data, pilots would hear a chime and see an amber light as well as a written message in the cockpit. Other aviation experts said that in severe turbulence, it can be virtually impossible for pilots to read their instruments.
The Airbus memo went out regarding all types of Airbus planes. Every major U.S. carrier flies Airbus planes except for Southwest and Continental.
Before it disappeared about four hours into its journey, failures in the plane's systems began to generate automated messages that were sent to the airline 10 minutes after the pilots sent a text message to Air France indicating they were encountering turbulence and thunderstorms.
Received during the course of three minutes, the messages indicated a growing series of electrical and equipment failures just before the plane disappeared, according to published reports. Some reports suggest the aircraft flew through electrically charged clouds and 100 mph winds.
"One of the things that puzzle me, and I think a lot of us, is the fact that we have 10 minutes that elapsed between the time the crew reported they were flying around cumulus nimbus buildups and the time this unraveling sequence began," said ABC News aviation consultant John Nance. "But there's one lesson from a lot of history of aviation accident investigations, and that is: It can look like two things are connected when, in fact, they aren't."
"Everything has at least one or two levels of backup and so something had to happen that started pulling these things offline one after the other because otherwise the aircraft would have been able to continue and at least be able to get to a diversion airport," said William Voss, director of the Flight Safety Foundation.
Air Comet Reports Intense Flash
Developments this week have confirmed the complexity of the puzzle as searchers pinpoint debris and assess the weather.
"I can't remember an accident in quite some time, if ever, that has raised the level of concern in the pilot community as much as this one has," Nance said.
"Those of us who are pilots are really apprehensive about what happened here because when you're out over the water at altitude, this sort of thing is never supposed to happen," he added.
Among those who are worried are a pilot and co-pilot with Spanish airline Air Comet, who said they saw something unusual Sunday night over the ocean. They reported an intense flash of light in the sky and have since filed a report with their supervisors, Air Comet's Fernando Gil confirmed to ABC News.
Air Comet 974 was flying from Lima, Peru to Madrid, Spain when "suddenly, we saw a strong and intense flash of white light in the distance, this was followed by a downward and vertical trajectory that broke up in about five or six seconds. We did not hear any communication of an emergency before nor after the incident," the pilots' report said, according to Gil.
Today Gil said the pilots encountered thunderstorms about five hours into their flight, which forced them to detour about 30 miles east of their intended route.
"The pilots filed their report shortly after landing and after learning of the missing Air France jet," he said. "They matched the time and place of the accident with what they had seen and immediately reported it in case the two events coincided. Their report was then handed over to the national aviation authorities."
The missing Air France plane is thought to have encountered severe thunderstorms and lightning or a combination of both. The four-year-old Airbus jet did have sophisticated radar that should have helped the pilots try to skirt any violent weather.
Ken Reeves, director of forecasting operations at Accuweather.com, said towering thunderstorms, fairly common over that area of the Atlantic, could have been a challenge.
"These storms go up and down at a fairly rapid rate, and so they can develop in the course of minutes," Reeves said. "They don't take hours or even days to develop. And they can diminish in the course of minutes as well. That makes the decision of the pilot ever so difficult determining whether to go around or through."
Reeves added, "Once you make that decision, unfortunately, many times you're committed, because you cannot turn back around because the storm may develop in front of you and behind you as well and you're kind of caught in the middle with nowhere to go but straight forward."
Air France 447: The Hunt for Black Boxes
Despite challenging terrain and recent setbacks, Chris Benich at Honeywell Aerospace, the company that made the black boxes, said he's optimistic searchers will find the black boxes -- provided they can locate the wreckage as a starting point.
"We have always been able to recover the recorder so we feel pretty confident we'll be able to do that," said Benich, director of aerospace regulatory affairs. "And there are a lot of folks from a lot of different agencies involved and out looking for them. We think we'll find them."
Benich explained that black boxes can survive a shockingly intense impact.
"If you think of this box travelling at 60 miles an hour and stopping in one inch, that would be about the deceleration force, and it will survive that type of deceleration."
The black boxes can also survive in up to 20,000 feet of water, and they emit a pinging sound. But water temperatures can affect the distance that sound travels, and the mountainous ocean floor can block the signal, which is only guaranteed to last about 25 more days.
The information the black boxes hold is critical: The cockpit voice recorder would have the last two hours of conversation recorded; the flight data recorder could hold information about as many as 400 systems on the plane to help investigators piece together the puzzle.
"We have to find that," Nance said. "This is a whole new class of airplane, not just the Airbus, but Boeings like it. We have to know what happened."
"It's down there," Nance said. "It'll be mangled, but it's down there."
"If they can't get that black box, they've got quite a detective story to sort out to try to determine the cause," said Robert Ballard, who discovered the Titanic and is now director of the Center for Ocean Exploration and Archeological Oceanography at the University of Rhode Island.
ABC News' Renata Araujo, Sonia Gallego, Joe Goldman, Christel Kucharz, Luis Martinez, Phoebe Natanson, Fabiola Antezana, Gabriel O'Rorke, Samira Parkinson-Smith, Kirit Radia and Christophe Schpoliansky, Reuters and The Associated Press contributed to this report.