Hand baggage restrictions imposed in the UK after an alleged terrorist plot to attack airliners are to be eased from Friday, the government has said.
The increased security levels have led to disruption
Passengers will still be limited to one item but its maximum size has increased to that of a small roller-suitcase.
The new size limit for carry-on luggage will increase to 56cm x 45cm x 25cm (22in x 17.75in x 9.85in approx), the aviation industry standard.
The limits have been blamed for causing delays and for costing airlines.
Most liquids will still not be allowed through security but instruments can be brought on board in a separate case.
Professional musicians had criticised the ban and some cancelled engagements rather than risk putting valuable instruments in aircraft holds.
The changes come after the government's transport security division held talks with the aviation industry on Monday.
The Department for Transport said the easing was designed to "lessen the burden on passengers, while maintaining a rigorous security regime".
But passengers should still allow extra time for security checks ahead of their flights.
"The measures we introduced in August were in response to a very real and serious threat which continues," it said.
British Airways, which has said cancelling more than 1,000 flights because of the alert cost it £40m, welcomed the announcement.
"This is a sensible step forward that takes full account of the security threat level while making life easier for our customers," it said.
A Virgin Atlantic Airways spokeswoman said: "We are pleased that the restrictions have been relaxed and we believe this is a step in the right direction."
Ryanair had earlier announced it was seeking compensation of about £3m from the government over airport delays resulting from the increased anti-terror measures.
The carrier said hand luggage size had been restored to the "safe and effective" norm but it still had concerns over "unnecessary queues" because of body searches.
"Hard-pressed frontline security staff are being forced to body-search families, elderly couples and young children as potential terrorists, when clearly they are not," it added.
Thousands of flights were cancelled at Heathrow and BAA's other UK airports after the alleged plot was foiled on 10 August.
A total ban on hand luggage was initially brought in but after a few days passengers were allowed to carry on a laptop computer-sized bag.
Electrical equipment will continue to be allowed on board, but larger items such as laptop computers must be removed for screening.
The current security measures ban all liquids except medication essential for the flight and baby milk and liquid baby food, which must be tasted by the passenger.
The Department for Transport said it was working on ways to ease this restriction in future.
Instruments which do not fit in the permitted cabin baggage size will now be allowed as a second item of cabin baggage, after being screened.
Transport Secretary Douglas Alexander said: "We will never compromise the security of the travelling public.
"The aim of the measures announced today is to maintain that security while lessening the inconvenience to passengers.
"I am grateful for the forbearance passengers have shown and assure them that we will keep these regulations under review."