United States military officials lost contact with hypersonic glider Falcon Hypersonic Technology Vehicle 2 (HTV-2), the fastest plane ever built, during a test flight over the Pacific Ocean on Thursday.

The Falcon HTV-2 cut out at 4:21pm BST, 36 minutes into its unmanned maiden voyage, leaving scientists and researchers scratching their heads and looking for the lost plane that would be capable of traveling from New York to Los Angeles in 12 minutes.

The Defense Advanced Research Projects Agency (DARPA) developed the plane as part of the Prompt Global Strike plan, to fly at speeds of 13,000 mph, while withstanding temperatures of more than 3500F caused by the ultrafast flow of air around the aircraft. It was the first plane to reach Mach 20- or 20 times faster than the speed of sound. The ultimate goal in designing it, DARPA said, would be the capability to reach anywhere in the world within one hour to respond to military crisis situations.

If the plan is ever realized, the Falcon would replace intercontinental ballistic missiles. Unlike missiles, the Falcon would be harder to detect and take down from the sky, making it a safer and faster to target potential terrorist sites.

The falcon was launched from the Minotaur IV rocket at Vandenberg Air Force Base in California. As expected, the spear-shaped plane detached from the rocket just as it hit the space barrier. The plane began its descent back into the atmosphere and was first reported to be on track. 20 minutes later, DARPA sent a message saying it had lost contact with the vehicle.

Scientists assume the plane used its automatic abort feature that would allow it to crash land into the ocean if it detected a glitch in the flight.

"More than nine minutes of data was collected before an anomaly caused loss of signal," DARPA said. "Initial indications are that the aircraft impacted the Pacific Ocean along the planned flight path."

Had the plane not lost contact, it would have glided into the airspace at 13,000 mph while preforming a series of technical maneuvers to test its aerodynamic performance- which can't be performed on the ground in a wind tunnel. The plane would have then (purposefully) landed in the ocean.

"'Here's what we know,'" Air Force Maj. Chris Schulz, the HTV-2 program manager for DARPA, said. 'We know how to boost the aircraft to near space. We know how to insert the aircraft into atmospheric hypersonic flight. We do not yet know how to achieve the desired control during the aerodynamic phase of flight. It's vexing; I'm confident there is a solution. We have to find it.'"

This is not the first time supersonic travel has gone awry. On April 22, 2010, the first Falcon test flight, HTV-1 was forced to make a premature landing in the ocean when computers detected a glitch after just nine minutes of flight.

Thursday's flight was meant to build off of the knowledge acquired form the first Falcon to gain crucial information on the plane's performance, including the resilience of its carbon composite body and navigation systems that were supposed to keep it on course as it moved at almost four miles per second.

But analysts are still confident that the flight was not a total failure:

"At this early stage of the game, if they did not experience failures, it's because they're not trying very hard," Defense analyst John Pike of Globalsecurity.org said.

Researchers still think it is possible to learn what worked and what failed on the flight, along with new information to add to the technical understanding of hypersonic flight.

DARPA has assembled a team to analyze the data collected during the first stages of the flight to help identify problems and perhaps reconfigure the policies, practices and decisions of future Prompt Global Strike flights.

Despite engineers' relative optimism, the loss is still a huge setback for the program. As of now, DARPA has only built two multimillion dollar Falcon prototypes, both of which have failed, and has no current plans to build anymore. Building another plane would be a huge technical and financial undertaking- launching from the Minotaur rocket alone costs between $15 and $30 million- let alone what it costs to actually design and build the plane.

The US military still has a long way to go before it can claim control over Mach-20, but many believe the research and trials will be well worth it in the end if it means a faster response to global crisis situations or terrorist threats.

You can stay updated with Falcon HTV-2 details by following #DARPA or #HTV-2 on Twitter.