Other UK airports now open after being affected earlier included Teeside, Leeds-Bradford, Blackpool, Sheffield, Manchester, Liverpool, Doncaster, Carlisle, Humberside, East Midlands and services in the Isle of Man.
Flights in and out of Dublin, the Irish capital, resumed at noon.
'Beyond a joke'
Airlines criticised the latest restrictions, which began at the weekend, saying they were overly cautious.
"The closing of Manchester airspace once again is beyond a joke," Richard Branson, the president of Virgin Atlantic, said in a statement.
He said test flights had "shown no evidence that airlines could not continue to fly completely safely".
British Airways said that the approach was "overly restrictive and not justified on safety grounds".
Jonathan Nicholson, a spokesman for Britain's civil aviation authority, called Branson's remarks "surprising" after a meeting last week in which airline representatives and engine manufacturers agreed to find a way to ensure planes could fly safely in the volcanic ash.
"We as an organisation can't just say, 'Oh, I'm sure it's all right, go fly', without evidence it's safe," he said.
Train operators Eurostar and Virgin Trains said they had added 10,000 seats to their services to help accommodate the disruption.
The volcano under the Eyjafjallajokull glacier in Iceland is continuing to erupt with no signs that the activity will end anytime soon.