Flights to and from USA are unaffected by the budget crisis and air traffic control, security, immigration and emergency services are operating normally. However some government-run tourist attractions and national parks are expected to be impacted by the situation so it's best to check before travel. At this stage, it is unclear as to how long the situation will last. If you are due to travel to the USA, you are encouraged to keep yourself informed of the Foreign and Commonwealth Office travel advice.
If you are travelling on a package holiday to the USA within the next 48 hours and a significant proportion of your holiday involves visiting a national park, please contact your tour operator or travel agent.