Transatlantic services from Britain remain suspended tonight, but the United States has lifted its aviation ban imposed after the terror attacks in New York and Washington.
Federal aviation officials gave the go-ahead for air travel in the United States to resume at 11.00am local time today (4.00pm BST), but warned travellers to expect slower operations and tight security.
Commercial and private planes are to be allowed to fly on a case by case basis. Officials urged passengers to check with airlines on flight schedules and available service, and allow ample time to deal with new security procedures.
In the UK, the government's temporary ban on planes flying low over central London is to be lifted from midnight on Saturday. The Docklands-based London City Airport - shut since Tuesday because of the restrictions - will open again tomorrow.
European transatlantic flights have restarted with an Alitalia flight from Rome. Dutch carrier KLM also has two America-bound flights leaving Amsterdam tonight.
The UK's two main transatlantic carriers, British Airways and Virgin Atlantic, were liaising with US authorities tonight in the hope of being able to start UK-US services as soon as possible.
Earlier, Canada allowed both BA and Virgin to fly back to Britain the US-bound planes that had been diverted to Canada on Tuesday.
Four British Airways flights that had been stuck in Canada were returning to Heathrow, while a fifth was flying to the west London airport having diverted to Bermuda.
Canada's ban, which originally grounded all flights, was lifted to allow the international return of diverted flights and to allow some internal flights. Air Canada said it hoped to begin a "limited schedule" of international services later today.
Meanwhile, American carriers are focusing on completing their international flights which had to be diverted on Tuesday to Canada and other locations.
Delta Airlines said that it expects its first inbound flights from Canada to arrive later today and intends to resume service from European cities tomorrow. However, the company said that the return to its full schedule of service would take a number of days.
United Airlines, two of whose jets were hijacked and crashed on Tuesday, confirmed it completed two of its diverted international flights this morning and would not begin any scheduled flights until 6.00pm CDT (12midnight BST)
BA flights to Tel Aviv, which had been suspended as Israeli airspace was closed, resumed this morning. BA have still suspended flights to Islamabad in Pakistan on the advice of the Foreign Office.
The shutdown of North American airports also hit Virgin Atlantic and the two airlines targeted by the terrorist attacks, American Airlines and United Airlines.
Bmi british midland's transatlantic services from Manchester were also cancelled, as was US carrier Continental's Stansted to New York service.
Airports operator BAA warned of massive disruption facing passengers for the immediate future. BAA, which operates a number of UK airports, including Heathrow, Gatwick, Stansted and Glasgow, said air travel would be subject to disruption and travellers would face increased security when American airspace reopened.
BAA urged passengers planning to depart from any British airport not to pack any sharp items in hand luggage, as stringent security meant anything from nail files to razor blades would be confiscated.
The extra security measures were so time-consuming that low-cost UK carrier easyJet cancelled a number of European flights. EasyJet has advised passengers that no hand luggage would be allowed on board.
