Tom Carroll, a retired engineer from Rockwell's Space Division, sent in this photo of "mystery contrails" that appeared in the LA sky on Monday night.
Experts are starting to weigh in and although there is no definitive answer yet, it appears a streak seen across the Southern California sky was probably just an airplane contrail.
The sight was first suspected to be a missile launch near Los Angeles on Monday night. A local television station showed video captured by a traffic helicopter around sunset. The location was reported to be west of Los Angeles, north of Catalina Island and approximately 35 miles out to sea, KFMB reported.
No one in the military was able to identify the object, NBC News Pentagon correspondent Jim Miklaszewski reported Tuesday morning. No branch had a military action planned, said Miklaszewski.
Vandenberg Air Force Base officials said the facility's last launch was a satellite on Friday. Naval Base Ventura County spokeswoman Teri Reid told the Los Angeles Times that the contrail did not originate at Naval Air Station Point Mugu.
On Wednesday, Pentagon officials told NBC that it's "satisfied" that the contrail was not caused by a missile but "likely caused by an aircraft."
"We have no evidence to suggest this was anything other than a contrail from an aircraft," said Pentagon spokesman Col. David LaPan.
"It's an airplane that is heading toward the camera and the contrail is illuminated by the setting sun," said John Pike, director of the U.S.-based security analyst group globalsecurity.org.
Jim Oberg, a former aerospace engineer who now consults for NBC, also agreed the sighting was most likely just an airplane contrail.
Pike also dismissed any theories that it was a secret military launch.
"If it were secret, we'd do it at night in Alaska where only the caribou could see it," Pike said. "It's an airplane contrail, pure and simple."
According to a statement from the North American Aerospace Defense Command (NORAD), the object is not a threat to national security.
"We are aware of the unexplained contrail reported off the coast of Southern California yesterday evening," NORAD told the Los Angeles Times. "At this time, we are unable to provide specific details but we are working to determine the exact nature of this event."