Just nine months after a Malaysia Airlines flight vanished, the puzzling loss of another passenger plane once again has highlighted an urgent question: How can modern jetliners simply disappear in today’s hyper-connected world?

As the search for AirAsia’s Flight 8501 off the coast of Indonesia entered its third day, aviation experts said the difficulty in locating the wreckage underscored the limitations in how planes are tracked, and showed how little has changed since the last disappearance.

Airlines use satellites to provide Internet connections for passengers, yet they still do not stream data in real time about a plane’s location and condition. As a result, Indonesian authorities have not been able to determine whether the plane, which carried 162 people, fell straight down or glided for miles before presumably crashing into the water, where search teams were converging.

The problems were compounded, experts say, by a lengthy delay in declaring an emergency after air traffic controllers lost contact with the plane, which slowed the search and rescue efforts.

“For basically an hour and a half they were struggling with the issue and not making any progress to initiate a search,” said Robert W. Mann Jr., an aviation consultant based in Port Washington, N.Y. “That’s a long time in that situation.”

No signs of the wreckage from the presumed crash were found on Monday, and the search resumed on Tuesday morning. Roughly 30 ships and 15 aircraft from at least four countries, including the United States, were involved in the search for the jet in the Java Sea, near the islands of Borneo, Java and Sumatra. Search teams, which included fishing boats pressed into service and vessels from Australia, Malaysia and Singapore, covered a large area of water near the island of Belitung, the last known location of the plane.

By contrast to the slowness of the response in both Asian disasters, experts said, air controllers in the United States today would probably sound an alarm within five to 10 minutes of losing contact with a jet.

“Everybody learned a lesson after the 9/11 hijackings,” in which some of the terrorists turned off the transponders that signal a plane’s location, said Peter Goelz, a former managing director of the National Transportation Safety Board. “So if that squawk suddenly goes off, it gets a lot of attention here.”

The delay in declaring an emergency, which also occurred after Malaysia Airlines Flight 370 veered off course in March, could have been because of a lack of training or bureaucratic fears about acknowledging a serious problem, analysts said.

Apart from the specifics of the two disappearances, the technological issues have been the subject of substantial debate among airlines all over the world.

Since the Malaysia Airlines jet disappeared, the International Civil Aviation Organization, which sets global airline standards, has been considering new rules on tracking planes. But the organization has moved slowly, primarily because it has been hard for the industry to reach a consensus, given the extra costs involved and how rarely crashes occur, Mr. Goelz said.

Most airline executives say there is no need for planes to constantly transmit their locations and that, with tens of thousands of planes in the air each day, such a deluge of data could cost billions of dollars. In addition to being tracked by land-based radar, most jetliners also have transponders, radios and text data-links that periodically send the plane’s coordinates and information about engine performance.

But some industry officials and many independent analysts say that the second such disappearance demands a response — and the sooner the better. They say the best compromise could be a system that would start streaming a nearly constant flow of such data whenever a plane deviated from normal flight parameters. These experts contend that such a system is particularly needed on transoceanic flights, where today’s large planes are often operating far outside radar range.

The issue first gained wide attention after an Air France jet crashed into the Atlantic Ocean in 2009 on a flight from Rio de Janeiro to Paris, and it took nearly two years for investigators to locate the flight data and cockpit voice recorders, the so-called black boxes that helped them reconstruct what had gone wrong with the flight.

Air France has since taken the lead in transmitting more data, programming its jets to send their positions, altitudes and fuel supplies every 10 minutes during normal operations and every minute in an emergency.

AirAsia recently began to improve the tracking of its fleet, but the plane that was lost this week had not yet been upgraded, The Wall Street Journal reported on Monday.

Under a timeline released by Indonesian authorities, radar and radio contact with the Airbus A320-200 jet was lost at 6:17 a.m. local time on Sunday morning, just five minutes after the pilots had asked to change their routing as they flew through an area with severe storms.

The air traffic controllers also received a final data transmission of the plane’s location at 6:17, and all contact was lost a minute later. But the controllers did not formally state that the jet’s position was uncertain until 7:08 a.m. or declare an alert until 7:28 a.m. They finally declared an emergency distress situation at 7:55 a.m.

No one knows what happened to the plane, though perils from the storm could have destabilized it or disoriented the pilots.

Mr. Mann, the aviation analyst, said that if the jet had been using a streaming or near-streaming data system, it would have transmitted more location data as the plane fell or glided toward the Java Sea, and that could have provided a more precise area to search for survivors.

Passenger jets are equipped with electronic locator transmitters that are supposed to broadcast their location when a plane crashes into the ground or the sea. But Indonesian officials have not detected any distress signal, either because the device malfunctioned or the AirAsia plane submerged too quickly for the signal to be heard. The officials have also not detected any pinging from the black boxes, which emit their own signals for at least 30 days even if underwater.

The battery life of the transmitters on most black boxes is likely to be extended to 90 days to increase the chances of recovery. But proposals to switch to black boxes that would be ejected during a crash, and could float on the water, have gathered more support in Europe than in the United States and Asia, analysts said.

Still, Mr. Goelz, the former National Transportation Safety Board official, said, “I think that with the enormous cost of these searches, and the uncertainty being so great, there will come a time for more action.”

Thomas Fuller contributed reporting from Jakarta, Indonesia, and Nicola Clark contributed from Paris.