An overnight technical problem resulted in flight delays at Scotland's main airports.
Edinburgh, Glasgow, Aberdeen and Prestwick airports were all affected by the issue at the Scottish Air Traffic Control centre at Prestwick, South Ayrshire.
Nats, which provides air traffic control services in the UK, said there had been interference on some radio frequencies used to speak to aircraft, affecting part of the Scottish airspace.
The airports affected later reported that operations were getting back to normal following the early morning delays.
In a statement, Nats said: "We apologise to passengers inconvenienced by the technical problem at the Scottish Air Traffic Control centre in Prestwick.
"The situation is continuing to improve and delays are reducing, however we recognise there are currently knock-on delays as a result of airspace capacity restrictions in place earlier in the day.
"We currently expect to meet demand for the number of flights planned for the rest of the day without creating any additional delay. We are also doing everything we can to safeguard the evening rush hour.
"Passengers are advised to contact their airline to confirm the status of their flight."
Edinburgh Airport said there had been no cancellations to its services as a result of the problem.
A spokesman said: "There are some delays and we expect there may be delays into the afternoon, but there are no cancellations and we understand that Nats have identified the problem."
Glasgow Airport said that while there are still some knock-on delays, operations are getting back to normal.
A spokesman said the situation is now "much improved on what it was earlier this morning".
He said: "There are still some delays but really it's just getting back to business as usual."
Aberdeen Airport initially said a small number of delays were affecting southbound flights.
It later tweeted: "The operation is getting back to normal with some slight delays this morning due to earlier air traffic system technical issues."
Scottish Transport Minister Derek Mackay told BBC Radio Scotland he believes the technical issue has been ''rectified and addressed''.
He added: ''However, there is a knock-on consequence to the airlines so people should check with their airlines and airports to ensure that their flights are running."