For two decades, Sacramento's light-rail system has been running on its own loop, unconnected to the greater train-travel world.

Until today.

At 10 a.m., amid balloons, banners and booming confetti cannons, the inaugural light-rail train is scheduled to roll into the downtown Amtrak depot, where it will dock side-by-side with bigger intercity trains to the Bay Area and with Amtrak's mainline cross-country trains.

That link will allow Sacramentans the opportunity to board light rail in their neighborhood, then switch at the depot for longer rail trips to the Bay Area and beyond.

The new line runs a mere half-mile from existing light-rail tracks on the K Street Mall to the back of the Sacramento Valley Station. But Regional Transit officials at today's opening ceremony at the depot from 10 to 11 a.m. say it signifies an important advance.

"This is a short extension in distance, but huge in terms of its symbolism," RT board Chairman Roger Dickinson said. "Sacramento now (offers) the option to get out of your car and onto public transportation to make a trip ... all around Northern California."

The opening also highlights what transit officials say is a still-missing link in Sacramento's light-rail system: The extension means Sacramentans finally can take trains directly to a major airport. But that airport is San Francisco International (via BART connection), not Sacramento.