Washington (CNN) -- President Barack Obama honored the nation's war dead in a Memorial Day speech upon his return from Illinois, after severe storms earlier in the day forced him to cancel his scheduled remarks at the Abraham Lincoln National Cemetery.
In a previously unscheduled appearance, Obama told military families at Andrews Air Force Base after flying back from a holiday weekend in Chicago that the nation owed them a debt of gratitude for their service.
"At its core, the nobility and majesty of Memorial Day can be found in the story of ordinary Americans who became extraordinary for the most simple of reasons: they loved their country so deeply, so profoundly, that they were willing to give their very lives to keep it safe and free," the president said.
His speech concluded a day of somber ceremonies and quiet reflection on the sacrifices of past generations. Earlier, after telling people gathered for his scheduled speech in Elwood, Illinois, to seek shelter in their cars from a heavy downpour, Obama visited the Hines Fisher House, a non-profit facility outside of Chicago that provides temporary housing for families of wounded veterans undergoing rehabilitation.
Vice President Joe Biden took part in the traditional wreath-laying ceremony at Arlington National Cemetery, followed by a speech in which he praised "the finest military the world has ever produced."
"Today is a day [in] which sorrow mixes with incredible pride," the vice president said. "We mourn those we lost and we hold fast to their memories. ... May God continue to bless the memory of all those who have died [so] that we may live."
Biden later paused to join mourners at Arlington's Section 60 -- the final resting place for many veterans of the wars in Iraq and Afghanistan. He was joined by Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff.
Many veteran and conservative bloggers took issue with Obama's decision to skip the annual ceremony at Arlington.
"On Monday, it's where the eyes of our entire nation will be focused," said Paul Rieckhoff, founder of the Iraq and Afghanistan Veterans of America. "And unfortunately, the president and his family won't be there to stand with us."
Obama's absence from Memorial Day services at Arlington is not unprecedented, but in recent years it has been a common practice to attend.
President Bill Clinton went every year of his presidency, and President George W. Bush went each year except for the year he was in Europe to commemorate the D-Day anniversary. Presidents Ronald Reagan and George H.W. Bush did not attend regularly.
In New York, a restored B-17G Flying Fortress bomber was scheduled to leave the American Airpower Museum airfield in Farmingdale and drop flowers into the waters of the Atlantic not far from the Twin Towers World Trade Center site.
The flight was meant to honor seven CIA personnel killed during a suicide attack at a military base in Khost, Afghanistan, in December.
"It is rare that we can publicly acknowledge the CIA's loss of brave men and women in the line of duty," said Jeff Clyman, museum president. "The knowledge that seven CIA personnel were killed at the hands of a terrorist compels us to pause and remember these patriots who fully understood the mortal danger they faced, and yet deliberately went into harm's way to protect our homeland and our lives."
In Washington, the Vietnam Veterans Memorial officially recognized six names added to the black granite wall in May. The addition brings the number of men and women killed or missing in action to 58,267.
Elsewhere, Major League Baseball games were scheduled to stop at 3 p.m. ET to observe the National Moment of Remembrance.
"Helping our troops is a cause very close to my heart, and I'm glad to see Major League Baseball will once again pledge their support on Memorial Day and beyond," San Francisco Giants pitcher Barry Zito said in a statement.
The moment -- established by Congress -- asks Americans to stop whatever they are doing and observe a minute's silence. The time 3 p.m. was chosen because it is when most Americans are enjoying their freedoms on the national holiday, the White House Commission on Remembrance said.
The idea for the moment was born when the commission director asked children touring Washington, what Memorial Day meant. Some of the children responded that it was the day the pools open.