Washington — As the summer travel season begins, the National Transportation Safety Board is urging parents to buckle baby carriers into airline seats instead of holding infants in their laps aboard planes.

Under current Federal Aviation Administration regulations, children younger than 2 can fly for free if they sit in a parent's lap.

"Saying it's OK to have a lap-held child sends the wrong message to parents. It's not OK to have a lap-held child in an aircraft," NTSB Chairwoman Debbie Hersman said. "The laws of physics don't change for babies. They need to be restrained, too."

The NTSB and the Association of Flight Attendants have tried for years to convince the FAA and airlines to require seats for all passengers, including babies. Still, many parents prefer holding their children for free instead of buying a ticket for them.

"It's unconscionable that it's allowed," former flight attendant Jan Brown said.

Brown was a crew member on a United Airlines flight that crashed in Sioux City, Iowa, in 1989. A 22-month-old boy was among the 112 people killed in the crash; his mother, who was buckled in, survived.

"Not all the love in the world could hold a child under those conditions," Brown said.

The FAA encourages parents to use child safety restraints, but officials said they aren't ready to make it a rule. The agency fears that parents will opt to drive to destinations rather than buying plane tickets for their babies, and FAA officials said they believe driving is more dangerous than flying.

"One thing we do know is that restraints save lives and that everyone needs to be restrained, especially our most vulnerable passengers, and those are our children," Hersman said.

Crash situations aren't the only danger, officials said, noting air turbulence can turn babies into projectiles.

Terra Converse, for example, was flying with her baby, Jake, on her lap and lost her grip during heavy turbulence. He flew out of her arms and slammed into the overhead compartment, but luckily suffered only minor injuries.

"I was scared to death," Converse said. "That was so hard not being able to protect him."