Travolta, an experienced pilot, flew the supplies to Baton Rouge, Louisiana, then toured the flooded city of New Orleans and visited rescue workers and shelters for evacuees. The two movie stars also brought along 400 doses of tetanus vaccines for rescuers.
The star of "Saturday Night Fever" and "Pulp Fiction" told AFP he was coordinating with Oprah Winfrey to get even more relief for the more than a million people affected by one of the worst storms in US history.
"That's our job today," he said. "We're hoping this time we're effective."
At the Jefferson Parish sheriff's command center, the two stars posed for pictures and thanked Church of Scientology volunteers administering tetanus shots to rescue workers. Both actors are Scientologists.
At one point, Travolta, 51, spoke quietly with Jefferson Parish Sheriff Harry Lee, then embraced him. Preston, 42, followed suit, with tears in her eyes.
"They've had such great loss," she said.
Travolta is the latest in a stream of sports, literary and entertainment celebrities to reach out to the victims of Katrina, the worst-ever storm to hit the United States.
Many have themselves been touched by the disaster. Rock and roll pioneer Fats Domino had to be rescued from his flooded New Orleans home.
Indianapolis Colts quarterback Peyton Manning and his brother Eli, of the New York Giants, were in Baton Rouge over the weekend distributing more than 14,000 kilograms (31,000 pounds) of emergency supplies, including diapers and bottled water. Their father, Archie Manning, was for many years the quarterback of the New Orleans Saints American football team.
Thriller writer John Grisham and his wife, Renee, who live in the stricken state of Mississippi, donated five million dollars to help relief efforts.
Others, such as Canadian diva Celine Dion, rapper Kanye West and crooner Harry Connick Jr, a New Orleans native, have been harshly critical of government responses to the disaster.
Travolta declined to join in the criticism, saying he had seen both good and bad.
"What we've seen in the shelters is wonderful, because people are being taken care of," he said. "What we've seen in the city is disastrous."