Hopes that UK flights would soon return to normal have been undermined by a second volcanic ash cloud in Iceland.
Chances to operate planes at many UK airports have been short-lived, and only a few flights have taken place.
Airspace in most of the UK remains closed until at least 0100 BST on Wednesday, but curbs have been eased in some northern parts of the UK.
Airlines said the restrictions were an overreaction, but the government said safety was its absolute priority.
David Shukman reports.
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