When longtime friends David Paine and Jay Winuk set out to encourage people to take part in volunteer and service projects on the anniversary of the Sept. 11, 2001 attacks, their goal was simple: to turn a day of unimaginable tragedy into a day for doing good.

Now, as the nation prepares to mark the 24th anniversary of 9/11, that lofty mission has evolved into a national day of service where people across the country participate in projects that honor the nearly 3,000 dead.

The nationwide effort kicked off Wednesday as thousands of volunteers began assembling packaged meals for needy New Yorkers in a festive atmosphere aboard the USS Intrepid.

Teams of volunteers filled small plastic bags with various ingredients for making a kind of jambalaya, including uncooked rice, dehydrated vegetables, lentils, salt and other seasonings, as a DJ blasted upbeat tunes from the wing of an aircraft carrier-turned-museum.

The two-day event, which runs through Thursday, aims to package more than two million meals for local food banks. It is among 25 large-scale volunteer service projects being organized in some two dozen cities across the country, including Atlanta, Boston, Chicago, Los Angeles and Seattle.

Overall, 9/11 Day estimates some 30 million Americans will participate in some form with the day of service, which Congress enshrined into law in 2009.

Beside meal packing, volunteers will be taking part in food and clothing drives, park and neighborhood cleanups, blood banks and other community events, the organization says. Even smaller acts of kindness count, like greeting strangers on the street or holding the door for someone.

"I think one of the inspirations clearly for this experience, 9/11 day was the way our nation was right after the 9/11 attacks. You know, when we weren't red states and blue states, we were just human beings helping one another and for me that was like the eye opening moment I guess when I realized that we're not nearly as divided as we think we are," said Paine.

James Lynch, whose father Robert Henry Lynch Jr. died in the 9/11 attacks, has volunteered the last two years at the event.

"I could think of no better way to honor my dad than to be here volunteering today . If he were here today , this is something that he would be doing and so us to be here in his name is just really special to all of us," said Lynch.