As a kindergarten teacher and a mother, Kathleen Tourtellotte knows something about children's safety. So when she and her husband, David, made plans to fly to Florida this summer, she decreed that their daughter, 15-month-old Emma, would travel the safest, not the cheapest, way.

Instead of carrying Emma for free on their laps, Kathleen insisted, they would pay $200 for a third airline seat, take along the baby's car seat and strap Emma into it between them.

The Clifton couple argued about the extra cost, David Tourtellotte recalled yesterday. "Fortunately, she won," he said.

The seating arrangement saved Emma's life four weeks ago when an engine exploded as their plane taxied for takeoff in Pensacola.

Yesterday, the Tourtellottes -- minus Emma, who was home sick -- testified on Capitol Hill in favor of legislation to require that children younger than 2 be buckled into airline seats as securely as Emma was, instead of sitting unprotected in their parents' arms. Airlines require children 2 or older to have their own seats, but younger children fly free if seated on a parent's lap.

Moments after Delta Flight 1288 began rolling toward takeoff July 6, the left engine flew apart.

Jagged metal tore into the plane, killing two members of a Michigan family in the row ahead of the Tourtellottes and injuring five other passengers.

A chunk of the fuselage fell on Emma, who was snuggled down in her $80 Century car seat. The high, gray plastic sides of the seat, not Emma, took the impact.

"There were pockmarks and dents on the seat," recalled Kathleen Tourtellotte, 31, in an interview yesterday. Blood from injured passengers covered the seat.

"The baby was screaming. In fact, we were all screaming," said David Tourtellotte, who with his wife escaped relatively unscathed. Twenty-two-pound Emma "had a scratch on her neck" and, aside from hardly sleeping for a week, has been just fine.

A National Transportation Safety Board investigator told Emma's parents that the car seat saved her.

"I wish today I had it to show you, but unfortunately, due to the damage and the blood that stained it, it had to be destroyed," David Tourtellotte, 31, an engineer, told members of the House aviation subcommittee yesterday.

The chilling experience of the Tourtellottes, who were invited to tell their story by Rep. Jim Lightfoot (R-Iowa), a safety-seat proponent, has fanned debate over how far the government should go to assure the safety of infants aboard airliners -- not only in crashes and other accidents but also during severe turbulence, which can catapult babies from their parents' arms.

The NTSB has investigated several such incidents, including one in January in which a father was knocked unconscious and the baby he was holding suffered bruises.

The Federal Aviation Administration urges placing children who weigh less than 40 pounds in child safety seats during flights but has not mandated any such measures.

FAA official Margaret Gilligan told the subcommittee yesterday that such requirements would drive families whose infants and toddlers now fly free away from relatively safe airline travel and onto statistically deadlier highways.

"Twenty percent of families would choose other modes of transportation," Gilligan said. "And that's the problem."

Critics of that argument counter that airlines would find a way to make the safer measures affordable rather than lose family business.

During yesterday's hearing, Jan Brown-Lohr, the chief flight attendant aboard the United Airlines DC-10 that crashed in Sioux City, Iowa, seven years ago, recalled what happened to the two "lap kids" aboard that flight.

Both were on the floor, according to airline regulations, and were being held down firmly by their mothers, who were braced for the crash. Both flew from their mothers' grips. One died. The other ended up in an overhead storage container 15 rows back but survived. CAPTION: Kathleen and David Tourtellotte, left, tell a House subcommittee that a child safety seat saved the life of their daughter, Emma, above, when an airplane engine exploded.