LOS ANGELES (CBSLA.com) — For $150 cash, a Pico Boulevard clinic with the green cross that symbolizes medical marijuana is apparently branching out.

CBS2’s David Goldstein confronted a doctor who handed Goldstein’s undercover producer a letter that would allow here to take her dog Cody on a flight for free – and it’s becoming big business.

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Emotional support animals are allowed by federal law to be taken uncaged on flights – your pet dog, a monkey, even a pig.

They’re becoming so common that some airlines and flight attendant unions say they may jeopardize safety for everyone on board.

“They can become unruly on board, can create potential problems for flight attendants who are trying to contain the problem when there may be a serious health emergency,” said flight attendants union Sara Nelson said.

Unlike trained service animals like 5-year-old Miss Kayla, ESAs need no training.

Glen Gregos of Woodland Hills, who uses a wheelchair because of a motorcycle accident, says the untrained ESAs could undo the thousands of dollars it took to train Miss Kayla to get him where he needs to go.

“If they become aggressive to my dog, it can ruin all of her training where she can’t assist me at all,” said Gregos. “It can stop their careers, so it’s a real thing.”

But the government does allow ESAs on board if passengers have documentation from “any licensed mental health professional,” including a medical doctor who is specifically treating a passenger’s mental or emotional disability.

And doctors are cashing in.

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After exposing one chiropractor who charged $250 for documentation even though the chiropractic board says it’s outside their scope of practice, Goldstein spoke to Howard Ragland, who runs a medical marijuana doctor’s office.

He instructed Goldstein via Skype on the diagnosis. (“So your dog gets you to relax, you’ll want to take him on the airplane, right?”) and was then given a letter generated by a computer and signed by another doctor, saying our producer had an “emotional/health related issue,” psychiatric complications, that would be greatly improved with the presence of a therapeutic companion.

A few days later, he didn’t have any answers.

Goldstein: “We sent in a producer who you talked to via Skype, You barely asked any questions. You didn’t ask how the animal would help her out and you authorized a letter and your people here took $150. You’re just selling these letters?”

The state medical board has filed an accusation against Ragland for negligence in issuing medical marijuana recommendations, and the Tulare County District Attorney’s Office has filed unrelated charges for issuing recommendations for patients he never saw.

He pleaded not guilty and is awaiting trial.

Gregos says the fake ESAs may look harmless, but for truly disabled people, they’re not.

“If the doctors are helping people have illegitimate dogs in public that are not trained specifically to help someone’s disability, it’s a real problem,” he said. “It’s a really bad ethical problem out there.”

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And federal transportation officials have taken notice, hoping to propose new rules later this year.