Republican presidential nominee Donald Trump's campaign plane (L) sits on the same tarmac as Democratic nominee Hillary Clinton's campaign plane (R), at Washington National airport in Washington, U.S., September 16, 2016. REUTERS/Carlos Barria

Republican presidential nominee Donald Trump hugs two Medal of Honor recipients before delivering remarks at a campaign event at the Trump International Hotel in Washington, D.C., U.S., September 16, 2016. REUTERS/Mike Segar

U.S. Democratic presidential candidate Hillary Clinton speaks at the Black Women's Agenda Annual Symposium in Washington, U.S., September 16, 2016. REUTERS/Carlos Barria

Trump supporters hold t-shirts refering to a comment made by Democratic presidential nominee Hillary Clinton ahead of a campaign event by Republican presidential nominee Donald Trump at the Trump International Hotel, in Washington, DC on September 16, 2016. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

Trump supporters hold t-shirts refering to a comment made by Democratic presidential nominee Hillary Clinton ahead of a campaign event by Republican presidential nominee Donald Trump at the Trump International Hotel, in Washington, DC on September 16, 2016. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

WASHINGTON, DC - SEPTEMBER 16: US Republican presidential nominee Donald Trump says US President Barack Obama was born in the United States during a campaign event at the Trump International Hotel, September 16, 2016 in Washington, DC. Trump invited former military veterans to speak during the event. (Photo by Mark Wilson/Getty Images)

WASHINGTON, DC - SEPTEMBER 16: Surrounded by military veterans, US Republican presidential nominee Donald Trump says US President Barack Obama was born in the United States, during a campaign event at the Trump International Hotel, September 16, 2016 in Washington, DC. Trump invited former military veterans to speak during the event. (Photo by Mark Wilson/Getty Images)

WASHINGTON, DC - SEPTEMBER 16: Surrounded by military veterans, US Republican presidential nominee Donald Trump says US President Barack Obama was born in the United States, during a campaign event at the Trump International Hotel, September 16, 2016 in Washington, DC. Trump invited former military veterans to speak during the event. (Photo by Mark Wilson/Getty Images)