Rust debris has begun falling from the structure, meaning passengers are using an alternative entrance to the terminal building.
The problem became apparent during the afternoon of 21 August.
Passengers on inbound Aurigny flights are instead having to use the entrance set up to keep social distancing during the pandemic.
The concrete legged control tower is several decades old and has a number of steel elements to it.
An engineering inspection will take place today, 22 August.
Work was due to be underway by now on the complete refurbishment of the airport, including lengthening the runway.
But it has been paused, after it came in £13M over budget.
More affordable alternatives are being considered.
ATR working to restore Aurigny's fleet capacity
Guernsey 'pushes ahead alone' and names Brittany Ferries as preferred sea link operator
Action urged over buried WW2 bombs in Guernsey
Guernsey's senior politician expects a long budget debate
Guernsey's population keeps rising
Condor calls out 'unacceptable delay' in Channel Island tender process
