Coastguard stations around the UK have been severely disrupted after a computer worm brought down IT systems.
The worm has hit all 19 coastguard control rooms
The Sasser worm has hit all 19 coastguard stations and the service's main headquarters, leaving staff reliant on paper maps and pens.
A UK Maritime and Coastguard Agency spokeswoman said search and rescue operations were not affected and there was no danger to the public.
British airways flights have also been delayed and BA call centres shut down.
Search and rescue
The Maritime and Coastguard Agency said staff had reverted to manual map reading as soon as its computerised mapping systems started to fail.
The paper-based system known colloquially as "pinkies", was in use before the service was fully computerised and had "served the coastguard well over many years," it said.
Swansea and Liverpool coastguards later said systems were coming back on line.
The Sasser worm has affected coastguard logging operations but left its command and control systems and lifesaving equipment unaffected.
Coastguards are still able to use telephones and radios but fax and telex machines have been put out of action.
British Airways also reported disruption and delays as a result of the computer virus which hit Terminal Four at London's Heathrow airport and call centres in Glasgow and Manchester.
The computers controlling the check-in, baggage handling and boarding of the aircraft all went down between 0815 and 0830 BST, said a BA spokesman.
The average take-off delay as a result was 10 minutes.
A total of 21 flights to Israel, the Middle East, the US and East Africa were affected but terminal was back to its normal timetable by 1200 BST.
The spokesman said the call centres in Glasgow and Manchester were still affected by the computer virus and all their calls had to be re-routed through to the Newcastle-based call centre.
British Airways receives an average of 20,000 calls nationwide every day.
The affected computers were all using Microsoft software - in particular the Explorer and 2000 packages.
Peter Dymond, head of search and rescue at the Maritime and Coastguard agency, said radio and other forms of communication with ships at sea were unaffected.
And the IT department was working hard to get the rest of the service back online, he added.
Liverpool coastguard, which covers much of Britain's west coast from Colwyn Bay to Mull of Kintyre, said the worm was causing major problems for its operations.
Falmouth coastguard, which is the main station for receiving information from abroad, said its work was being hampered by the problem.
And Great Yarmouth coastguard said the worm was causing "great inconvenience".
The Sasser worm infects computers via the internet
A coastguard spokeswoman said the worm had brought systems down on a relatively quiet day.
"The most problems we are experiencing are on an administration level," she said.
Staff were all fully trained in using paper maps instead of computer systems, she added.
The coastguard service is the latest casualty of the worm, which is thought to have affected millions of Windows PC users since it was first discovered on 1 May.
Unlike recent viruses, Sasser does not travel by e-mail but makes its way around the internet unaided.
It can infect PCs running Windows 2000 and Windows XP that are not protected against the system loophole it exploits.
According to anti-virus firms, machines running Windows 95, 98 and Millennium Edition can help spread Sasser even though they cannot be infected by it.
Sasser is called a worm rather than a virus because it searches out machines to infect by itself without any help from users.
So far, four variants of Sasser have been seen, the fourth of which - Sasser D - scans so aggressively for new computers to infect that it can cause networks to become congested with data and slow down.
The worm has spread rapidly around the world, causing disruption wherever it strikes.
Taiwan's national post office said 1,600 of its machines were hit by the virus which forced more than 400 of its 1,200 branch offices to revert to pen and paper.
The disruption left customers queuing in long lines at many of the company's offices, according to television reports.
Two Hong Kong government departments and some hospitals on the island were hit by Sasser.
In Australia, Railcorp trains were halted apparently because a computer problem disrupted the radio systems and stopped drivers talking to signalmen.
Also in Australia, Westpac Bank staff were forced to use manual methods to record transactions as the worm made computers unusable.
And Finnish company Sampo temporarily closed all its 130 branch offices as a precaution against Sasser.