U.S. Navy crew members on board a P-8A Poseidon aircraft assist in search and rescue operations for Malaysia Airlines Flight 370 in the Indian Ocean on Sunday, March 16. The Boeing 777 went missing during March 8 flight from Kuala Lumpur to Beijing as it entered Vietnamese airspace. 
Indonesian national search and rescue agency personnel watch over high seas during a search operation for missing Malaysia Airlines Flight 370 in the Andaman Sea on, March 15. 
A foam plane with personalized messages dedicated to people involved with the missing flight are placed in the viewing gallery at Kuala Lumpur International Airport, on March 15, in Sepang, Malaysia. 
A member of the Malaysian navy makes a call as its ship approaches a Chinese Coast Guard ship during an exchange of communication in the South China Sea on March 15 in Kuantan, Malaysia. 
A Indonesian search and rescue ship heads to the Andaman Sea during a search operation for the missing Malaysian plane in the Indian Ocean, near the tip of Sumatra Island, on March 15. 
Elementary school students pray for the passengers aboard the missing flight during class in Medan, North Sumatra, Indonesia, on March 15. 
Col. Vu Duc Long of the Vietnam air force fields reporters' questions at an air base in Ho Chi Minh City after a search operation for Malaysia Airlines Flight 370 on Friday, March 14. 
Members of the Chinese navy continue search operations on Thursday, March 13. The search area for Flight 370 has grown wider; after starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, efforts are expanding west into the Indian Ocean. 
A Vietnamese military official looks out an aircraft window during search operations March 13. 
Malaysian air force members look for debris on March 13 near Kuala Lumpur, Malaysia. 
A relative of a missing passenger watches TV as she waits for the latest news in a hotel in Beijing on March 13. 
A member of the Indonesian National Search and Rescue Agency scans the horizon in the Strait of Malacca off Sumatra island, Indonesia, on Wednesday, March 12. 
Relatives of missing passengers wait for the latest news in a hotel in Beijing on March 12. 
Journalists raise their hands to ask questions during a news conference in Sepang, Malaysia, on March 12. 
Indonesian air force officers in Medan, Indonesia, examine a map of the Strait of Malacca on March 12. 
A member of the Vietnamese air force checks a map while searching for the missing plane on Tuesday, March 11. 
Iranians Pouri Nourmohammadi, second left, and Delavar Seyed Mohammad Reza, far right, were identified by Interpol as the two men who used stolen passports to board the flight. But there's no evidence to suggest either was connected to any terrorist organizations, according to Malaysian investigators. Malaysian police believe Nourmohammadi was trying to emigrate to Germany using the stolen Austrian passport. 
An Indonesian navy crew member scans an area of the South China Sea bordering Indonesia, Malaysia and Thailand on Monday, March 10. 
Vietnam air force Col. Le Huu Hanh is reflected on the navigation control panel of a plane that is part of the search operation over the South China Sea on March 10. 
Relatives of the missing flight's passengers wait in a Beijing hotel room on March 10. 
A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews before returning to search for the missing plane Sunday, March 9, in the Gulf of Thailand. 
Members of the Fo Guang Shan rescue team offer a special prayer March 9 at Kuala Lumpur International Airport in Sepang, Malaysia. 
A handout picture provided by the Malaysian Maritime Enforcement Agency shows personnel checking a radar screen during search-and-rescue operations March 9. 
Italian tourist Luigi Maraldi, who reported his passport stolen in August, shows his current passport during a news conference at a police station in Phuket island, Thailand, on March 9. Two passengers on the missing Malaysia Airlines flight were reportedly traveling on stolen passports belonging to Maraldi and an Austrian citizen whose papers were stolen two years ago. 
Hugh Dunleavy, commercial director of Malaysia Airlines, speaks to journalists March 9 at a Beijing hotel where relatives and friends of the missing flight's passengers are staying. 
Vietnamese air force crew stand in front of a plane at Tan Son Nhat airport in Ho Chi Minh City, Vietnam, on March 9 before heading out to the area between Vietnam and Malaysia where the airliner vanished early Saturday. 
Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9. 
The Chinese navy warship Jinggangshan prepares to leave Zhanjiang Port early on March 9 to assist in search-and-rescue operations for the missing Malaysia Airlines flight. The Jinggangshan, an amphibious landing ship, is loaded with lifesaving equipment, underwater detection devices and supplies of oil, water and food. 
Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9. The vessel is carrying 12 divers and will rendezvous with another rescue vessel on its way to the area where contact was lost with Malaysia Airlines Flight 370. 
The rescue vessel sets out from Sanya in the South China Sea. 
A family member of missing passengers is mobbed by journalists at Kuala Lumpur International Airport on Saturday, March 8. 
A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported March 8. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10. 
Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8. 
Malaysia Airlines official Joshua Law Kok Hwa, center, speaks to reporters in Beijing on March 8. 
A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8. 
Wang Yue, director of marketing of Malaysia Airlines in China, reads a company statement during a news conference at the Metro Park Lido Hotel in Beijing on March 8. 
Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8. 
A woman asks a staff member at the Beijing airport for more information on the missing flight. 
A Malaysian man who says he has relatives on board the missing plane talks to journalists at the Beijing airport on March 8. 
Passengers walk past a Malaysia Airlines sign on March 8 at Kuala Lumpur International Airport. 
Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference on March 8 at a hotel in Sepang. "We deeply regret that we have lost all contacts" with the jet, he said.
- Bill Palmer: Deliberate acts are not the only possibility in disappearance of Malaysia flight
- He says it's not clear what systems, such as ACARS, were turned off and when
- Palmer: Descent reported might be from 777 adjusting to no autopilot, not deliberate act
- Palmer: Much of 777 behavior could be from built-in systems reacting; guessing inadequate
Editor's note: Bill Palmer, an Airbus A330 captain for a major airline, is the author of "Understanding Air France 447," an explanation of the details and lessons of the crash of that aircraft in June 2009.
(CNN) -- Those trying to draw conclusions from the information trickling from the investigation into the disappearance of Malaysia Airlines Flight 370 should go carefully.
It is plausible that, as Malaysia's Prime Minister asserted, the plane's flying for hours after losing contact with air traffic control was "consistent with deliberate action," but it's not the only logical explanation of the airplane's bewildering trajectory.
Statements that the Aircraft Communications Addressing and Reporting System was intentionally disabled, for example, leave out the fact that the ACARS is required to send the satellite contact requests (so-called "handshakes") that, according to news reports, were reported to have occurred for hours after the flight's disappearance.
The plane has multiple functions and channels connected to the ACARS and at least some of it must have still been working.
For example, one part of this communications system is used for messages between the airplane and air traffic control (clearances, position reports, etc). Another is used to communicate, essentially with text messages, between the airplane and the airline. Messages can also be sent automatically for maintenance functions such as reporting faults and sending routine engine data. The range of functions that would have been available for someone to disable is not yet clear.
And at least one news report described altitude excursions between 45,000 feet and 23,000, which one pilot suggested might have been done willfully to render passengers unconscious. But this strikes me as behavior that would also be consistent with the airplane flying completely unattended with the autopilot off. Though these oscillations are larger than I might expect, it would be a natural behavior for the airplane to fly relatively large but gentle pitch oscillations.
This would be true especially if the airplane's auto-throttles were also for some reason disabled. There have been statements made that such changes could only be made by a skilled aviator, but what "skilled aviator" cannot hold altitude within 20,000 feet?
Incapacitation or something else that could prevent the crew from controlling the plane -- fire, collision, explosive depressurization -- could also be indicated, which wouldn't necessarily mean the cockpit was breached by anyone.
The airplane reportedly made "suspicious turns." However, it is the nature of those turns that will reveal if it was deliberate "heading" (directional) changes or if nobody was flying the airplane at all. If the autopilot was off and the airplane was essentially flying on its own, I would expect a variety of heading changes. These changes could be initiated by turbulence during flight.
If the airplane's routes were controlled intentionally by selecting the heading or by programming the flight management computer, the flight path would be very straight, then a turn that would last usually from 10 to 30 seconds, followed by more straight flight.
The mystery of Malaysia Air 370 
Why so many watch plane coverage 
Malaysia Air 370: facts vs. speculation While a close-up analysis of the flight path would be required to determine the case, it seems that officials are not even sure if the flight path headed northwest toward Pakistan or southwest into the vast Indian Ocean.
On the technical side, the Boeing 777-200ER is a fly-by-wire airplane -- that is, movement of the controls is converted into electrical signals that interact with flight-control computers and instruct the plane's control surfaces on the wings and tail. Its characteristics may be able to explain much of the airplane's behavior.
With the autopilot off, the airplane will adjust the pitch (the up or down movement of the nose of the plane) to maintain a speed set by the pilot. It will pitch up if it's going faster than the desired speed and pitch down if slower. This is called pitch trim. Anyone who has flown even a small aircraft will be familiar with this concept. Therefore, when disturbed, it will fly a series of pitch changes as it settles down on the trimmed airspeed.
Pitch protections built into the system ensure that the airplane never goes too fast or too slow. Temporary input on the control wheel, or changes in the airplane's weight as it burns off fuel, temperature and other normal atmospheric changes along the course can initiate the altitude changes as the airplane continues to seek its trimmed speed.
Heading changes are also what I would expect to see in an autopilot-off situation. The 777's fly-by-wire roll control law controls the tilt of the wings. The airplane would be subject to atmospheric disturbances that could act to tip a wing up every now and then, but built-in protections prevent the plane from exceeding bank angles in excess of 35°. While a conventional airplane would tend to spiral down in that situation, the 777 incorporates automatic pitch compensation, so the airplane could easily hold its altitude in these turns.
The fly-by-wire control system on the 777 makes it a very stable airplane, capable of flying for hours with the autopilot off without crashing.
If the flight path can be shown to be very straight lines with neat turns followed by another straight line, then I would throw out the "autopilot-off" theory, but it seems as though officials can't even determine where the plane was heading, much less the nature and cause of some heading changes.
The consistent theme in the mystery of this flight has been very little data, and the exact nature of that scant data is vague and changing.
Whatever exact scenario can account for the possible incapacitation or deliberate actions of the crew, the loss of the transponder and other communications and the airplane's mysterious flight path is likely to be a situation we have not seen before.
I would urge that we not jump to conclusions based on inconclusive evidence. The evidence we have may be "consistent with deliberate acts," but it is also consistent with other explanations as well.
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The opinions expressed in this commentary are solely those of Bill Palmer.
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