Fireworks, flyovers and a Trump speech ahead as US celebrates 250th

President Donald Trump will lead a "spectacular rally" on the National Mall in Washington DC to celebrate America's 250th anniversary. The event, organized by a White House-backed public-private partnership, will feature flyovers by hundreds of aircraft, fireworks displays, and a speech from Trump. Concerns exist about the potential for crowd size due to extreme heat and thunderstorms, as well as air pollution caused by the large firework display. The event has been criticized by some Democrats who accuse Trump of politicizing the celebration.