Land's End Airport will remain closed until at least next Wednesday, after more rain left the grass runway waterlogged again.
Skybus, which operates daily flights to and from the Isles of Scilly, has only flown from Land's End on one day in the past month due to saturated ground.
Passengers have all been diverted via Newquay Cornwall Airport on every other day since December 14 thanks to the weather.
The airport problems started soon after the closure of Penzance heliport, which left the planes as the only form of passenger transport between west Cornwall and the islands.
More rain forecast over the next few days have yet again forced the Isles of Scilly Steamship Company, which owns Skybus, to divert its planes.
A spokesman for the company said: "On a number of occasions we have been on the cusp of being able to resume passenger flights from Land's End only for more rain to fall. The situation is frustrating but during December we received almost 50% more rain than average so the ground remains very wet. We are continuing to explore longer term solutions to hardening the runway but for the next week have opted to fly via Newquay in order to give certainty to all our passengers. As soon as we can resume flying from Land's End we will."
The spokesman added that some Skybus aircraft may use Land's End in the next few days for routine training and maintenance flights. These aircraft will not be carrying passengers.
Skybus has apologised for the inconvenience and all passengers are being notified. Anyone planning to travel during this time can contact Skybus on 0845 710 5555.