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

US President Donald Trump will head to Washington DC's National Mall on Saturday for what he has billed as a "spectacular rally" celebrating America's 250th anniversary. The event, taking place as a sweltering heatwave grips swathes of the eastern and central US, will include flyovers by hundreds of aircraft and a fireworks display organisers hope will be the biggest of all time. Military flyovers over Washington DC will happen every hour between 13:15 local time (17:15 GMT) and sunset, the organisers said, and Trump's new Air Force One will feature in one of the formations over the capital. The president, however, has been accused by opponents of politicising the nation's anniversary event and several music acts dropped out soon after being announced. Extremely hot, humid temperatures of approximately 38C (100F) and a later-than-anticipated start time may also have an impact on the size of the crowd that attends. The intense heat has already led to events being cancelled. On Friday, organisers of the National Park Service's Independence Day Parade in Washington DC said they had cancelled the annual event over ​safety concerns. Some celebration events have also been cancelled from