Video posted on YouTube by Trailspotter
Air ambulances are unable to land at Addenbrooke's Hospital in Cambridge after its helipad was destroyed by a military aircraft.
It means critically ill patients can't be flown directly to the hospital, but have to be taken to Cambridge City Airport instead.
Addenbrooke's is the major trauma centre for the East of England and its helipad is used by the East Anglian Air Ambulance, Magpas Air Ambulance and Essex and Herts Air Ambulance.
The helipad is currently out of use after it was wrecked during a training exercise by the US Air Force.
Watch the full video on YouTube by Trailspotter
Dr Victor Inyang, Medical Director of East Anglian Air Ambulance: "Due to an incident at the Cambridge University Hospitals helipad involving a military aircraft on Wednesday 21 April the helipad is temporarily unavailable to air ambulances.
"The next closest helipad is at Cambridge City Airport, where one of the East Anglian Air Ambulance (EAAA) teams is based.
"It will be possible for the EAAA helipad to be used as an alternative landing site during this time and have patients transferred to Addenbrooke’s from there by land ambulance.
"Addenbrooke’s is the major trauma centre for the region, therefore quick and efficient transfer of critically ill or injured patients to the hospital is vital.
"Using the EAAA helipad is the best alternative while the CUH helipad is reinstated."
Maj Keavy Rake, from the USAF 48th Fighter Wing, said: “The area was surveyed according to our policies and procedures and some damage did occur.
"We are taking steps to rectify as soon as possible.
"Our units are continuously coordinating with our local partners to improve operations. We are greatly appreciative of the relationship and coordination we have with the U.K.”
One eye witness said he's never seen anything like this before.
It all unfolded in front of me. I saw debris flying up in the air, my biggest fear was the helicopter. The worry was if the debris went above the rotor it could have damaged the aircraft or, even worse, the people. I’ve been all over the place across the world, but I’ve never seen anything like this.
A spokesperson from Cambridge University Hospitals said: “While our normal helipad is being repaired air ambulances will temporarily land at nearby Cambridge City Airport and patients are then transferred to the hospital in road ambulances with critical care staff on board, meaning we can continue to see and treat them as normal.”