It is not known when the familiar sight of its yellow helicopters will be appearing again in Norfolk's skies, but today the region's air ambulance insisted it was 'business as usual'.

The East Anglian Air Ambulance (EAAA) has had to bring in two replacement red helicopters, after its normal yellow craft were grounded by the company which operates them.

The EDP understands that Sterling Aviation, which is based at Norwich International Airport, temporarily suspended its operations on Friday, after a key member of staff left the company.

This meant the two helicopters Anglia One, based at Norwich Airport, and Anglia Two, based at Cambridge Airport, were grounded over the weekend and yesterday.

The charity quickly activated its contingency plan and on Sunday and Monday brought in aircraft supplied by an alternative operator, Bond Air Services, with one based in Norwich and another in Cambridge.

A spokesman for the air ambulance said the whole operation would be 'cost neutral' to the charity and stressed there were no air ambulance missions over the weekend anyway due to adverse weather conditions across East Anglia.

Steve Whitby, deputy chief executive of the EAAA, added: 'There have been rumours over the weekend that our service has been suspended and I want to take this opportunity to reassure all those who support us that this is not the case and, in fact, it's very much 'business as usual'.'

It has also emerged that the air ambulance bought one full engine and the core of the second engine in the two yellow helicopters.

With a value of �500,000, the two engines are leased back to Sterling and the charity said the company was up-to-date on its payments as part of this agreement.

The temporary aircraft are Bolkow 105s, a type of aircraft widely used for air ambulance work around the UK and the rest of the world, and which were still regularly used by the EAAA as back-ups to their BK 117 helicopters.

The EAAA's partners at Essex and Hertfordshire Air Ambulance Trust and at the East of England Ambulance Service are fully aware and supportive of the move it has made to ensure the continuity of its service.

The charity said it hoped the yellow helicopters, which are a key part of its brand, would only be out-of-action in the short-term.

Sterling Aviation refused to answer the EDP's questions, and would only confirm that it had temporarily suspended its operations and was working with the CAA and its customers to resume normal service as soon as possible.

The CAA also declined to comment, saying negotiations were still ongoing with Sterling.

For more information about the East Anglian Air Ambulance, contact the charity on 0845 066 9999 or visit its website at www.eaaa.org.uk