A multi-million pound appeal has been launched to buy a second emergency medical helicopter for London.

The capital only has one air ambulance, which was unavailable for 55 days last year due to maintenance requirements, so Mayor Boris Johnson and London’s Air Ambulance are now calling for Londoners to donate so a new helicopter can be bought to continue being able to provide a speedy life-saving service.

London’s Air Ambulance is a charity and has already raised £1.6m towards the Your London, Your Helicopter campaign but an extra £4.4m is needed by July 2015 in order to buy and sustain a second helicopter, which will extend daylight flying hours for five years.

The charity and its skilled advanced trauma team of doctors and paramedics has been operating for 25 years and has treated over 32,000 critically injured people, often performing roadside surgery.

The Your London, Your Helicopter campaign sticker

Operating 24/7, a helicopter is used during the day and rapid response cars at night or in adverse weather conditions.

By having another helicopter they will be able to extend summer daylight flying hours, reaching an estimated 400 more patients per year by air.

Graham Hodgkin, CEO of London’s Air Amublance, said: “When London’s current, and only, emergency medical helicopter is offline for servicing or maintenance, our patients need us to have recourse to a second helicopter immediately.

“We deliver advanced trauma care 24/7 but we want to ensure we can get to our patients as quickly as possible during daylight hours. £4.4 million might seem like a large amount but if everyone donates just £5 today we could have your helicopter in the air by the summer.”

Boris Johnson added: “London is the greatest city in the world and is also one of the most generous cities in the UK. We rightly rally together to rapidly raise millions for disasters in other countries around the world but on this occasion the need is right here on our doorstep. London needs a second emergency medical helicopter - that’s why I’m asking that if you possibly can please rally together and support this fantastic campaign.”

Donations of £5 or more can be made online.