London Air Ambulance struggled last year when its only emergency medical helicopter was unavailable for nearly two months.
It left the capital with no Air Ambulance for 55 days last year due to maintenance requirements.
The charity says they urgently need a second helicopter to provide cover to make sure this doesn't happen again.
The Air Ambulance is aiming to get the help London businesses as well as the public to donate the £4.4 million needed by July 2015.
The money raised will be used to acquire and sustain a second helicopter and extend daylight flying hours for five years.
The London Mayor, Boris Johnson said:
“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.”
Donators can see exactly where the money is going, literally, as when the money is paid the site will show exactly what part of the new helicopter has ben paid for.
Captain Neil Jeffers, Chief Pilot at London’s Air Ambulance is told us more about their new campaign.