(CNN) Boeing has issued operational guidance to airlines as investigators continue to probe what happened to Lion Air Flight 610, which crashed into the Java Sea last month, killing all 189 passengers.

In a statement on Tuesday, the airline manufacturer said it had issued an "Operations Manual Bulletin" advising airline operators how to address erroneous cockpit readings.

A spokesperson for Boeing wouldn't disclose to CNN whether the directive was issued to operators of all Boeing aircraft, or just those who fly 737 MAX 8 planes, the same model as Flight 610.

The directive points operators "to existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor," the statement said. "Whenever appropriate, Boeing, as part of its usual processes, issues bulletins or makes recommendations regarding the operation of its aircraft."

An AOA, or angle of attack, sensor is a vane that sits outside of the aircraft and gives pilots a visual reading of the plane's angle of attack -- or "the angle between the oncoming air or relative wind and a reference line on the airplane or wing," according to Boeing.

"It is very important because it tells them if the plane is flying at too high angle of attack, which can lead to an aerodynamic wing stall (loss of lift)," said aviation analyst and editor-in-chief of Airlineratings.com, Geoffrey Thomas.

Boeing said that the Indonesian National Transportation Safety Committee had "indicated that Lion Air flight 610 experienced erroneous input from one of its AOA (angle of attack) sensors."

Boeing is involved in the ongoing investigation with the Indonesian National Transportation Safety Committee and other government authorities into the Lion Air crash and "continues to cooperate fully and provide technical assistance."

Photos: In photos: Lion Air plane crashes off Indonesia A relative of one of the crash victims tosses flower petals from an Indonesian Navy ship on Tuesday, November 6. Hide Caption 1 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Victims' families and colleagues react on a Navy ship as they're ferried to the crash site on November 6. Hide Caption 2 of 27 Photos: In photos: Lion Air plane crashes off Indonesia An Indonesian official examines a turbine engine from the plane on Sunday, November 4. Hide Caption 3 of 27 Photos: In photos: Lion Air plane crashes off Indonesia People in Jakarta grieve over the coffin of a relative on November 4. Hide Caption 4 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Indonesian Navy divers recover a flight data recorder on Thursday, November 1. Hide Caption 5 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Families of the victims look through personal items that were recovered from the wreckage. Hide Caption 6 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A police officer arranges shoes recovered during search operations. Hide Caption 7 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A Navy ship arrives at a search area in the waters of Karawang. Hide Caption 8 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A relative of a passenger cries at a Jakarta hospital on Tuesday, October 30. Family members have been providing authorities with DNA samples to help identify victims of the crash. Hide Caption 9 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Officials transport a body bag in Jakarta. Hide Caption 10 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Indonesian President Joko Widodo inspects debris. Hide Caption 11 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Victims' relatives embrace at a police hospital in Jakarta. Hide Caption 12 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Soldiers drag ashore an inflatable raft containing debris from the plane. Hide Caption 13 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A wallet is seen in the water where the plane went down. Hide Caption 14 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A relative of a passenger cries at a hospital in Jakarta. Hide Caption 15 of 27 Photos: In photos: Lion Air plane crashes off Indonesia President Widodo (front row, second from right) tours the operations center in Jakarta where debris is laid out. Hide Caption 16 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Police work to identify personal belongings that are believed to be from the plane's wreckage. Hide Caption 17 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A police officer studies a map in the search-and-rescue command center. Hide Caption 18 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A diver with the Indonesian Navy enters the water off the north coast of Karawang. Hide Caption 19 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Rescue workers carry a body that was recovered from the waters near Jakarta on October 29. Hide Caption 20 of 27 Photos: In photos: Lion Air plane crashes off Indonesia A woman in Pangkal Pinang prays as she and others wait for news on October 29. Hide Caption 21 of 27 Photos: In photos: Lion Air plane crashes off Indonesia People gather on the beach as a rescue team prepares to leave the coast of Karawang. Hide Caption 22 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Wreckage from the plane lies at a port in Jakarta. Hide Caption 23 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Bagus Sunjoyo, head of airport authority for Soekarno-Hatta International Airport, speaks to members of the media during a news conference. Hide Caption 24 of 27 Photos: In photos: Lion Air plane crashes off Indonesia People watch a rescue team as a helicopter flies overhead. Hide Caption 25 of 27 Photos: In photos: Lion Air plane crashes off Indonesia People look at the passenger manifest for Lion Air Flight JT 610. Hide Caption 26 of 27 Photos: In photos: Lion Air plane crashes off Indonesia Merdiana Harahap is consoled in Medan, Indonesia. Her husband was on the plane. Hide Caption 27 of 27

Following Boeing's bulletin, the Federal Aviation Administration (FAA) announced on Wednesday it would issue an airworthiness directive to Boeing 737 MAX 8 crews if they experience the same problems that brought down Lion Air Flight 610.

In a statement it said, "The FAA has alerted affected domestic carriers and foreign airworthiness authorities who oversee air carriers who use the 737 MAX."

The FAA directive does not acknowledge an issue with the entire fleet of 737 MAX 8 airplanes -- the same model as Flight 610 -- and there have been no reported comparable issues in the US.

Problems on the last four flights

The Boeing statement comes amid a number of significant developments in the investigation into the fatal airline disaster, following the discovery of Flight 610's flight data recorder last Thursday.

Investigators who analyzed the Flight Data Recorder (FDR) after the October 29 crash uncovered the issue, said Tjahjono. The finding is the first technical problem revealed as part of the investigation into why the plane crashed.

"We are formulating, with the NTSB (US National Transportation Safety Board) and Boeing, detailed inspections regarding the airspeed indicator," said Tjahjono, on Tuesday.

Lion Air Group Managing Director Captain Daniel Putut Kuncoro Adi told CNN on Wednesday that Lion Air strictly follow Boeing's guidance for operating the 737 MAX 8s, as laid out in the maintenance manual book.

"Pilots write in the logbook about the problem they had in the flight, then our technicians fix it and write (what) they did in the logbook," said the managing director, adding that technical conversations between pilot and technician regarding the aircraft are written and signed in a document called the Aircraft Flight and Maintenance Log.

However, analysts have asked why the plane wasn't grounded earlier, when the problem with the air speed indicator issue first surfaced.

"The question is why wasn't this plane pulled from service and the problem system removed," said Geoffrey Thomas.

Lion Air Group's managing director told CNN that Boeing's maintenance manual does not provide instructions to ground the aircraft, even if they encounter a repeated problem.

"As long as we fixed the problem and the technician declares that aircraft is safe to fly, the pilot will fly the aircraft, because that means the aircraft is safe to fly," said Captain Daniel Putut Kuncoro Adi.

Plane was intact when it crashed, investigators say

Lion Air Flight 610 was intact with its engines running when it crashed at high speed into the Java Sea, Tjahjono said Monday.

Tjahjono said that due to the small size of the debris found and loss of the plane's engine blades, investigators determined that Flight 610 did not explode in the air, but was in "good shape" before it crashed 13 minutes after takeoff.

Some of the families of the victims aboard Flight 610 were taken by boat to the crash site location on Tuesday to pray for their loved ones and view the recovery process in-person, Muhammad Syaugi, head of Indonesia's Search and Rescue Agency said.

He said that his team was still working to locate the cockpit voice recorder (CVR), which he believes is buried under the deep mud.

After initially hearing a "ping" from the CVR on Saturday, diving teams could no longer hear a signal from the device.

Meanwhile, the plane's other black box, the flight data recorder, was located Thursday, and investigators said it showed Flight 610 had performed 19 flights -- including its final flight.