BELMONT, Calif. (AP) _ The newborn found abandoned in a jetliner restroom will remain in county custody at least until Friday, a juvenile court commissioner ruled Monday, rejecting the father's effort to obtain custody.

The parents of 5-day-old Alyssa Frances LoCasto, Louis and Christina LoCasto of New York City, attended the closed hearing but declined to talk with reporters. Christina LoCasto, 24, has pleaded innocent to a felony charge of child endangerment.

Vicki Yeley, Louis LoCasto's lawyer, said the couple decided over the weekend to remain together, and that decision was one reason why Juvenile Court Commissioner Patricia Bresee decided against placing the child in her father's custody.

''Mr. LoCasto is very much in love with his little daughter,'' Yeley said. ''He is also very much in love with his wife. The family has made a decision to stay together. They are determined to remain united.''

The commissioner asked both LoCastos and a court-appointed attorney representing the baby, Gerry Hilliard, to return to court Friday after the San Mateo County Department of Social Services compiles a report on possible homes for Alyssa.

Until then, the couple will be allowed to visit their infant daughter under the county's supervision.

Mrs. LoCasto is accused of delivering the baby in the bathroom of a San Francisco-bound United Airlines jet shortly before takeoff from Newark, N.J., last week, and leaving the child under the sink, wrapped in a bloody towel.

She was released from custody after posting $50,000 as bail. If convicted, she faces up to six years in prison.

The LoCastos, who have been married since 1986, had planned to vacation in California with their other two children when the incident occurred.

The infant, 8 pounds 9 ounces at birth, will remain in a foster home until at least Friday.

She was released Saturday from Mills Memorial Hospital in San Mateo, 15 miles south of San Francisco, where she was taken after a custodian found her on board the plane. She is under the supervision of the San Mateo County Child Protective Services.

Hilliard said Alyssa ''appears to be a normal 5-day-old ... suffering no ill effects from what occurred'' despite spending six hours in the restroom.

Hilliard asked Bresee to keep Alyssa in the custody of the Department of Social Services for the time being, but said he was unsure what position he would take on Friday, when the report would be presented.