Aurigny will be operating a single plane on routes to and from Alderney until the end of April.

Passengers trying to fly between the islands have experienced disruption on-and-off since Wednesday 13 April.

In a lengthy post on its Facebook page, Aurigny has explained the technical reasons behind the problems and says lessons have been learnt.

It operates two Dornier aircraft on the routes and both were bought new over the past five years, but recently, neither has been continuously available, which it says is "highly unusual."

One aircraft was undergoing an annual maintenance check in Guernsey and Aurigny says it should have returned to service two weeks ago:  

"However, a small number of components needed to be replaced and unfortunately the manufacturer did not have any of the required parts in stock and had to manufacture them.

After waiting for the manufacturing, the parts were delivered to us at which point we realised that (they) had manufactured the wrong parts.

We are now waiting for the correct parts to be manufactured and in the meantime, the aircraft remains in our hangar in an unserviceable condition. When the correct parts are received the aircraft will quickly be returned to service which we expect to be on 28th April."

The second Dornier developed a problem with part of its avionics system. Avionics are based in the cockpit and are responsible for control, monitoring, communication, navigation, weather and anti-collision systems. 

As the two Dornier aircraft are similar, Aurigny hoped it could swap the component from the grounded aircraft:

"Unfortunately, the component on the aircraft in the hangar was a different part number and the manufacturer advised us that we could not use it on the other aircraft. The supplier did not have the component we needed in stock, so we ordered one from the supplier in the USA.

The part was shipped using FedEx as they were the only courier company that the part supplier would use." 

Aurigny says the new part wasn't due to arrive until Bank Holiday Monday but in the meantime, the manufacturer said the avionics part could be swapped between aircraft, with some changes to software settings. This was done and the aircraft re-entered service on Friday (15) only to face fog disruption. It developed a similar technical fault after only one flight on Saturday but has returned to service today (19).

The airline says that it has learnt from these events:

"The avionics component that failed on the second aircraft has not failed previously on either of our aircraft in the five years we have been operating this variant of the Dornier 228. Given the $50,000 cost of this component and its history of good reliability, it is not something that we would routinely stock in our parts inventory.

However, we could all but remove the impact of any future failure of this component or its equivalent on the other aircraft if we harmonised the systems on both aircraft. We will now work with the manufacturer to explore that possibility."

To maintain the service, Aurigny tried to charter alternative aircraft and a larger passenger ferry but none were available. Instead, it chartered small local boats and laid on extra Guernsey Southampton flights. It apologises to everyone who has been inconvenienced:

"We know and understand that our customers rely on us to get them to and from Alderney. We will continue to work hard to ensure that our customers can travel."