During a training exercise, the US Air Force CV22 Osprey tiltrotor damaged the matting of the helipad from the ground as it took off from Addenbrooke’s Hospital on Wednesday.
Video posted online shows military personnel leaving the aircraft before it takes off and debris is sent flying.
Now, critically ill patients are currently unable to use Air ambulances services to the site, which serves as the East of England’s major trauma centre for three air ambulance crews.
They are instead being airlifted to Cambridge City Airport and making the large leg of their journey by ambulance.
Repair work is under way, with the East Anglian, Magpas and Essex and Herts Air Ambulance services confident it will be back in use soon.
Maj Keavy Rake, of the USAF’s 48th Fighter Wing, said:
Several of the tiltrotors, which operate like helicopters, are based nearby at RAF Mildenhall in Suffolk.
A spokesperson for the ambulance services said:
A spokesperson for Cambridge University Hospitals NHS Trust added that they were still treating patients “as normal”.