Snow had to be cleared from the runway at Durham Tees Valley Airport
Council managers on Wearside say they have only enough supplies of grit to last for five more days if the current cold snap continues.
Sunderland Council said it had used 12,000 tonnes of grit so far and had just 2,500 tonnes left.
But it told road users it had ordered a further 9,000 tonnes.
Across Wearside and County Durham almost 100 schools remained closed on Friday, with some warning they would still be shut next week.
Commuters faced further disruption, with rail services and flights from Durham Tees Valley Airport liable to delay and cancellation.
A blanket 30mph limit has been imposed on the A1M between Northumberland and North Yorkshire because of treacherous ice.
Durham County Council has already restricted gritting operations to preserve stocks.
The authority said it would continue treating A and B roads for as long as possible but it was coping with "very difficult" weather conditions.