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.
Reprimanded Guernsey Deputy criticises 'absurd' length of disciplinary process
How Guernsey remembers...
Guernsey's Chief of Police retires in a week
