The parents who reported last week that their 6-year-old son may have been on board a giant, runaway balloon could potentially be in more trouble with the Federal Aviation Administration for making a phone call than for setting loose the saucer-shaped craft, aviation experts say.

Most FAA rules on the release of unmanned balloons, rockets and kites don't take effect until aircraft or property are put in danger or the craft enters restricted airspace.

Hobbyists don't even need a pilot's license to fly an engine-less craft weighing less than 155 pounds.

Most likely, analysts say, the FAA is focusing on a phone call it received from the boy's father, Richard Heene, who reported the out-of-control aircraft was loose.

"That's what they're going to be looking at, that call," said Joseph Gutheinz Jr., a retired Army pilot and former FAA and U.S. Department of Transportation inspector. "If this guy was calling the FAA reporting a false emergency, and that disrupted other air traffic, that would be the bigger issue here."

SLIDESHOW: View photos from the alleged hoax

Richard and Mayumi Heene reported last week that their son Falcon was in the escaped balloon hurtling through the air as millions watched on live TV. The boy was later found safe at the family's Fort Collins home, and authorities say they believe the balloon scare was a hoax. The FAA is saying little about what it is investigating.

The balloon episode caused a brief disruption at Denver International Airport last week, with some planes sent to different runways as a precaution, but no flights were grounded.

If authorities determine the phone call was a hoax, the U.S. Department of Transportation could pursue a federal criminal case.

Mary Schiavo, a former inspector general for the Transportation Department, said she suspects the FAA will wait for local law enforcement to figure out whether the Heenes' reports were intentionally false.

"They have to prove intent for a criminal case," Schiavo said.

Larimer County Sheriff Jim Alderden said he expects to recommend charges including conspiracy, contributing to the delinquency of a minor, making a false report to authorities, and attempting to influence a public servant. The most serious charges are felonies and carry a maximum sentence of six years in prison.

Alderden said authorities also would seek restitution for the costs of the balloon chase, though he didn't provide a figure.

FAA Spokeswoman Laura Brown said violating federal balloon rules could result in penalties that "could be anything from a warning letter to a civil penalty."

"There's not a lot more we can say about the investigation right now," she said.

Brown wouldn't say how long the investigation could take or what possible fines would be. The FAA typically levies large fines only against commercial airlines that break federal safety rules. Its largest fine ever was $10.2 million against Southwest Airlines last year for flying planes that had missed critical safety checks, though that fine was later reduced to $7.5 million.

Gutheinz said he doubts the FAA knows what to make of the alleged Heene hoax. Agency investigators spend most of their time reviewing large operations, not investigating kooky episodes that grab the public's attention.

"Every once in a while you get a drunk pilot, or a student flying a plane they're not supposed to fly, but nothing like this," he said. "This is just something no one's ever imagined happening."