President Barack Obama tried to allay safety concerns on Wednesday as millions of Americans began traveling for the long Thanksgiving weekend, emphasizing that authorities had ramped up airport security in the wake of the Paris attacks. The president said government officials knew of “no specific and credible” threat at home, but advised Americans to be vigilant about any suspicious activities. New York City’s annual Macy’s Thanksgiving Day Parade was expected to attract as many as 3.5 million people, according to organizers. Police Commissioner William Bratton said the city would deploy more officers in anticipation of the record-breaking crowds. Nearly 46.9 million Americans are also expected to travel over the holiday weekend, which is considered the busiest U.S. travel holiday of the year.