LOS ANGELES — Slowly surmounting a key obstacle, the shuttle Endeavour maintained a heading Saturday through the streets of Los Angeles toward its retirement home at a museum.

Endeavour's final mission began when it departed from the Los Angeles International Airport before dawn Friday, rolling on a 160-wheeled carrier past diamond-shaped "Shuttle Xing" signs.

Friday evening it stopped as crews spent hours transferring the shuttle to a special, lighter towing dolly. Then around midnight, it traveled over a bridge across Interstate 405, an especially tricky part of the complicated journey because of the size of the space craft and width of the bridge.