Obama arrived at San Francisco International Airport late this afternoon and was whisked off to a Democratic fundraiser at the Westin St. Francis hotel.
From the top of the staircase leading down from Air Force One, which touched down at 4:53 p.m., Obama gave a quick wave to a small crowd awaiting his arrival at the airport. The president then made his way down the stairs to an awaiting motorcade.
The fundraiser, which consists of a dinner and a reception, will raise money for Organizing for America, Obama's political arm of the Democratic National Committee.
On its way to the hotel, the motorcade complicated traffic as it weaved through downtown, and created tensions as it crossed the intersection of Sixth and Mission streets at about 6:15 p.m.
Police tried to keep people from crossing Sixth Street and many didn't know why the street was blocked off. Dozens of frustrated pedestrians waited on the corner.
One middle-aged man defied police orders and stepped off the curb only to be pushed back by an officer, causing the man to fall onto the sidewalk.
However, when the president's motorcade approached, the crowd's animosity evaporated, replaced by cheers.
A silhouette could be seen waving from inside one of the limousines.
By the time the motorcade reached Union Square, hundreds of protesters and onlookers had gathered. Obama is not conducting any public appearances during the one-day visit but many tonight wanted him to hear their messages on various issues, including the war in Afghanistan and health care reform.
"I'm here to save my patients and my profession," said Dr. Ali Rezapour, a physician at St. Mary's College of California in Moraga.
"The biggest barrier between a doctor and a patient ... are the insurance companies," he said.
"This white coat should never have been put in the place of discriminating between the haves and the have-nots," said Rezapour, who was wearing his white doctor's coat.
Rezapour said he was disappointed in Obama's work so far on national health care reform and urged Obama to initiate a single-payer system.
"George Bush didn't break my heart. He (Obama) can," Rezapour said. "I put my hopes in him and, unfortunately, he has disappointed me on many issues."
Jo Boatman, of San Francisco, said she also supports single-payer health care, and the removal of "every single" soldier from Afghanistan.
"I'm totally against war," she said.
Boatman said that though she did not vote for Obama, "he's reneged on almost everything" he promised in his campaign.
The president is scheduled to leave Friday morning.
Until he departs, the Federal Aviation Administration is enforcing flight restrictions around San Francisco.
The restrictions are in effect between 4:50 p.m. today and 10:05 a.m. Friday and affect a 30-mile radius of San Francisco International Airport, according to FAA spokesman Ian Gregor.
Private pilots will be unable to take off from or land at SFO, Oakland International Airport and Hayward Executive Airport at certain times, Gregor said.
One local flight school, Oakland Flyers, has expressed frustration of the restrictions, saying it stands to lose more than $2,500. The school says it has sent an invoice to the White House.
"Because of the no-fly zone, we can't do basic training of students, we're on hold until the president leaves town," said Jeff Reeder, an instructor at Oakland Flyers. "We can't do anything, we're effectively shut down."